There were a couple still on her back. Those I sort of scootched off or they came off on their own when I removed mom.
When I separated my V. spinigerus brood there were still quite a few on her, but at least half the brood had already left, and they were all fluorescing so I knew they were fully hardened and ready to separate. I brushed them off of her (gently) and moved mom so I could safely rehouse everyone.