I do not handle any of my rats, I clean cages but the handling comes down to grabbing the rat putting it in a holding tub while cleaning it's tub, none of my rats bite, the key is/was that from the start there was a ZERO tolerance policiy for bitters and chewers, a female bites her and her litter are culled.
Again to have a good colony holding back the BEST of the BEST is important and if you do you won't have to handle any rats.
This is my policy as well. Minimal handling, very selective breeding.