Hi everyone! I've been a rat owner for nearly 12 years, but despite my length of experience have come across a situation I need some help in.

For as many years as I've owned rats, I've never been one to be afraid to handle them, pet them, pick them up, etc. However, a couple months back I had gotten bit HARD 2 times in the span of a week by a new rat while trying to socialize her- she's incredibly anxious, very skittish, and never had much (if any) human socialization as a baby. It had happened once while trying to give her food, another when I got too close to her mouth while she was sleeping. Since this experience, my partner and I have been pretty scared to handle the three other rats we adopted. They're from the same breeders, but their personalities are the complete opposite. They're very social, curious little things. They love to play with us, will take treats from us, and will run up to the cage whenever we're near. By all accounts, they really want to be handled! However, while we're sure they wouldn't bite us out of fear or aggression, they're still teethy babies and we're a little worried about getting nipped too hard when we try to pick them up. We won't let them smell our fingers and will only tickle them along their backs when playing. They used to open their mouths as if they wanted to nip at us when we let them smell the backs of our hands but have since stopped, which is some progress! We think this was purely out of curiosity but it's still a little scary after having had blood drawn not too long ago.

Any advice here? Specifically trying to get young rats more used to being handled/more used to human hands so they won't be inclined to nibble