So I have had Sia and Sheena for a about 4 months now and haven't really seen much if any improvement on the two. Sia is probably the one who trusts me at least a little bit. She will sit on my shoulder/back and be fine without freaking out. But if I try to pick up Sheena or handle her she will run away or escape which results in a little glider hunt to get her back into the cage.

I've been doing bonding by way of a bonding pouch and mimicking tent time by using a blanket. I also feed them treats regularly and talk to them as much as I can but I still get crabbed at all the time by Sheena.

Do you guys have any idea how I can get these little ones to trust me enough to handle them?

I don't know that you can really substitue tent time with a blanket. The whole idea is that you have a safe, totally enclosed area by using a tent. They can't run away or escape and are kind of forced to interact with you.
Some gliders are just explorers and don't like to be held. Two of my three would much rather explore than sit with me lol. Most gliders don't like being picked up either -

Gliders generally do NOT like to be held. That is definitely why you use a tent to bond. If you are trying to hold on to her then she is not going to trust you. Try getting a real tent and work with them everyday.