I have quite a few adults that will approach me directly when their vivs are opened, because they are hungry and are ready to come out NOW. This can be intimidating.
If a snake is defensive or afraid, it will generally retreat and try to hide (often rattling or whipping its tail) or stay put and rattle and/or threaten to strike. If it is in a threatening posture, I put my hand down quickly flat over the head, which makes it so the snake can't bite, and then proceed to take it out of the viv. It the snake is actively running away, I approach it quickly and confidently and take it out. The more you try to "soothe" it and offer your hand for it to smell, or whatever, the more likely you are to get bitten. Just get the snake out as quickly as possible, with the minimum amount of fuss.
The snakes that come forward to be taken out- you kind of have to know the snake. I have some that are in such a hurry to eat they will strike at anything that moves, and a true feeding strike from an adult is not pleasant (but you won't die, either). If I think a snake is going to fly out and bite, I will hook train the snake so my hands don't have to touch it, either until it is out and "safe," or all the way through the process of weighing and placing in the feeding container.
Obviously the safest way to handle feeding time is to thaw the mice, place in feeding containers, and then thoroughly wash your hands to remove any trace of mouse smell. Snakes still know, though, that it's feeding time, and are going to be on high alert.
You can even train snakes to come to the front of their vivs to be removed for feeding. My hatchlings are all trained to come to the front when I knock on the bin. Generally they know it's feeding time and are lined up, but if someone is not present and waiting I'll tap on the front of the bin. (Usually while I'm a couple snakes before ready to feed the missing one, to give them a minute to respond.) If the snake still doesn't come out, there's a good chance they are blue, and shouldn't be fed anyway.
Regarding snakes that are defensive about coming out; once out, I handle the snake until it is no longer nervous or fearful, definitely not just a short period of time. I'm more inclined to handle longer if the snake is not comfortable being handled, rather than shorter.