I think that a lot of it is simply temperment of the chins, which is something you breed for. I have some chins that have never been handled a lot, but meet you at the door and love scritches, and I have some that are kind of crazy no matter what you do.
I handle my to check them about each day for the first week or so, then every so often, maybe once a week or what not, to just check them. Overall on my herd, I'll randomly pull chins out just to make sure they're okay, check them over, feel them to make sure they're not too thin or something that I can't readily see when looking at them.
All of my kits get handled the same, you don't know when they are born what will be better quality than others. Some will have more potential, but you can't really tell until they get older.