There are quite a few options,hopefully people will add to this thread as time goes on,but this works.
You will need a container that you can seal,choose a size according to the scorpions size,but you want it to be a fairly snug fit both because you don't want the scorpion moving around much,and to save on shipping if there are several scorps you need to post. The plastic tubs used for salads,or sauces are cheap,or free if you save them from your shopping or fast food,you want food safe tubs so no chemicals or gasses are released by the plastic. I also save the postage boxes I receive the scorpions in,and other small sturdy boxes that look suitable to post tubs in.
There are several options when it comes to packing the tub,coir peat(mulled coconut fibre,no additives),sphagnum moss,and tissues or unscented toilet paper are usual,I prefer sphagnum moss or tissues,or both.
Wet some tissues or moss and squeeze it out by hand,moisten about 3/4 of what you think it will take to fill the tub. How moist you leave it depends on species and the estimated travelling time,but generally squeezing out as much moisture as you can by hand is fine. For rainforest or mesic species you may not want to squeeze out as much as you can,but it shouldn't be wet,just damp,if I'm worried it's too dry for a species I might put one small,fairly wet piece of moss or paper somewhere at the edge of the tub rather than have the whole lot too damp.
Fluff the moss or tissue out a bit and put it in the tub,it should look full,but loosely packed.
Hollow out a space in the middle of the tub for the scorpion,making sure the bottom is still covered.
Add dry moss or tissue over the top of what you have and try the lid so you can see if more or less needs to be added,you want a fairly solid layer over the hollow,but not enough that you have to force the lid down or have trouble closing it,I like to tuck stray pieces in and adjust it before I have an angry scorpion in there! When you open the lid,hopefully you can pull the top layer off as a mat. When using tissue you can fold or bunch it ready to put on top,so you don't really need it as a mat,but it's easier imo.
Now comes the fun part,getting the scorpion into the hollow in the tub!
At this point I like to set things up in a large container or tub on the floor or table,it contains any mess,and the scorpion if things go wrong! If you're trying this for the first time I strongly recommend it,if only to calm your nerves.
Callum has written a good tutorial on handling scorpions,read it here - http://www.scorpion-forum.com/t8418-how-to-correctly-handle-a-scorpion
Personally I have coaxed the scorpions onto spoons,tipped them from a bare rectangular tub,held so the corner is like a pouring spout so you can direct the scorpion,or lifted them by the metasoma with padded tongs (you risk damaging the scorpion lifting it by the tail,but for some it may be the safer option done carefully,for scorpions with a relatively high body weight having the body supported by a spoon or a flat smooth object is a good idea.)
Arrange everything in the tub so it is all comfortable to access,the container the scorpion is coming from,the container it's to go in,the lid and your topping material. I recommend placing the lid upside-down with the topping material on it,but arrange it however you feel you can get the material and lid on quickly,you could hold it in your free hand.
Tip the scorpion from the spoon or tub,directing it so that it runs forward into the hollow and quickly cover it with the topping material and put the lid on. In my experience most will stop moving once covered with moss or tissue but get the lid on quick! Sometimes a scorpion will try to climb out of the hollow,but I've always had time to cover it and get the lid on. Remember the edges of the hollow are soft,and nothing is packed down solid,so there's not much chance of damaging the scorpion unless it gets right to the edge of the tub,in which case you can hold that side of the lid up and try to coax it to move backwards with an implement. Failing that,you may have to catch it again,that's where setting everything up in a large tub takes the pressure off,both you and the scorpion can relax for a bit and try again. I've never had to do that but it's nice to know I wouldn't have to be in a panic chasing it around the room!
Hopefully now you have a scorpion nested in a bed of moss or tissue,not squashed or cramped,but cushioned and insulated on all sides,keeping it safe,not rattling around or moving around in a tub getting bumped and at risk of damage if the parcel is treated roughly.
Scorpions have a very slow metabolism,they use very little oxygen so ventilation is not needed. The main danger is the media drying out and the scorpion desiccating if postage is delayed or if the weather is particularly drying. So at this point unless you are using a container with an airtight screw lid you should write the species name on the lid (it avoids confusion) and wrap wide tape several times around the seal making it absolutely airtight.
You also want to make sure the lid cant come off in transit,some people like to wrap tape both around the seal and from top to bottom.
Another reason to have the tub sealed is one suspected by Mark Newton and I recently,it seems my local post office uses insecticide as part of pest control,scorpions in non-airtight containers arrive dead regardless of moisture levels,whereas there's been no problem posting to other areas,and no problem with sealed containers coming to me,by process of elimination,it would appear insecticide is to blame.
How you pack the tub for postage is up to you,it will depend on the size of the tub,how many to one address,and the standards or regulations for postage where you live.
In my case,I wrap the tub in bubble wrap (saved from received parcels) and put it in a cardboard box(saved!). I fill the spare space in the box with more bubble wrap,or stuff it tight with crumpled newspaper. Then the box is posted in a sealed,padded postage bag.
If conditions in your area,or the area you are posting to are particularly harsh,you might consider filling the space with a material with higher insulation properties such as synthetic 'cotton wool' type wadding,or even Styrofoam cut to fit. You might want to consider packing the tub into a 'foamy' such as used when posting live fish in extreme conditions,maybe even adding heat pads,although excess heat can be more dangerous than a slow cooling.
I've used this method with a 100% success rate,with scorpions spending up to five days in the post. Only once have have I received a dead scorpion packed this way,and that was because the tub wasn't sealed properly and the tissue was bone dry.
I mentioned coir peat,the method is the same,only all of the peat is damp,squeezed out as much as possible,and none placed on top of the scorpion.
Of the materials I mentioned,I prefer sphagnum moss. Sphagnum moss is available from most places that sell gardening supplies,and there's a surprising amount in a compressed bag. It's a useful thing to have on hand if you keep animals,and can be boiled to reuse it.
One thing I find it really useful for is to supply water to inverts without them or their prey (suicidal crickets!) drowning in the water dish.
Copyright Dave Dunn,04/02/2016
Hopefully this is helpful to some of you,and I hope others detail their methods