I don't know too much about dwarf hamsters. I only have syrian hamsters, but I'm sure some of the things between them are similiar.
If you training your hamster to eat out of your fingers, practice feeding them large pumkin seeds, and then you can count on your fingers not being bitten. Praise them after they did it. It is a good way to encouraging them.
To keep them out of the food bowl, just spend some time each day and watch them eat, and if they get inside the bowl - take them out. Do it each time for several days. They will get the hint that it is not okay for them to do that.
If they bite a lot, tap them on the nose each time. They don't like it, and they will remember that feel.
I hope these ideas will help.