We experienced the same thing with my boyfriends glider, Yuki. Funny thing is, my glider doesn't give a hoot if you stick your hand in there and pick him up. What we've found is, he simply gets scared when there is suddenly a gigantic hand in there searching him out!
If you can find a way yo comfort them and let them know your hand isn't something scary trying to get them, then they will slowly learn to trust you reaching in there.
Try speaking softly to them before you open the pouch. Then slowly open up the pouch (keep talking to them!) and let them see it is you. Don't stick you face right there and scare them, but be at least a foot away, and just let them see its you as you talk to them. Then very slowly show your hand and start to reach in to pick them out. Eventually they should learn you are not scary.
This worked for us. Hope it helps you!