I need help.

I'm at my wits end. I've tried so hard to bond with my gliders, and they're doing okay, but the biting isn't stopping. They're around 3-4 years old and I've had them for two months as of today, and their previous owner never corrected the biting. This is also the man who fed them fruit loops.
I don't want to get rid of them, and I won't, but I just want to cry. They don't lunge at me or crab, it's just a curious hard bite. I know they don't mean to hurt me, and that they just want to see what I'm all about, but we have a few good days and then I get chomped and I'm scared of them all over again.
Please help. I've tried the 'psst' sound, and it rarely works anymore. I don't use lotions or hand sanitizers too often, and when I wash my hands I wash them with clean water before trying to touch them.
Thankyou.

Zoey responds to the "tss", I get it back from the sassy little fuzzbutt sometimes... But for the most part, she stopped biting me in a week or so.
Have you tried licky treats?

Try:
Make the pzzt sound very emphatically in their face.
Gently blow in their face (this must be done at the exact time they bite, if dont after the bite they wont get it)
Distract them with a toy.
This one is real hard: ignore the bite (when they realize it gets no reaction, they may stop)

I would NOT distract them with food as they MAY learn that bite=food(reward)

I do not like the idea of licky treats to stop biting, although some say it works.

I had read that it may teach them to lick instead of biting... Sorry, Don't want you to be glider chow. Some people will give a VERY gentle bop/tap on the nose to distract the glider... I never had to do that, So i don't know how well that works. The "Tss" worked with Zo.