It's not necessary, but if your snake has had previous bad sheds, it is a helpful precaution. I see no reason not to spritz the enclosure a little extra in order to make the shedding process easier for your snake.
60% is fine as long as your BP is shedding completely. By completely, I mean even a few large pieces. If it's sticking and not able to shed everything off, then you should bump the humidity the next time around, but I wouldn't expect any problems.