Ok, sounds good. I would stick to small mice then. I'm guessing she is definitely under 200 grams still, so small mice (12-17 grams) should be great. As far as wet mice, I just give them a quick pat with a paper towel and in they go. My guy strikes every time with this technique, but has ignored the prey that is not "freshly" defrosted every time, hahaha!!
I like that you're trying to get into the snake mentality, it helps with all animals to try to think like they might, to think about their primitive minds and apply that knowledge to our every-day care for the animals. It will help as you continue to learn your snakes body movements, mannerisms, etc... Their body language is the only way they can "communicate" with us, so we need to learn from them in order to provide the best care for them. It'll also help to learn the warning signs and avoid being needlessly tagged.
Yeah, braining is gross and should be closer to a last resort.
I can see a scale being low on the priority list, there's a lot to buy when getting started. Any kitchen scale will do the trick. Mine is a Mainstays brand from Walmart (under $20). I suggest a big "plate" so you can put a large enough Tupperware or container on it to fit your adult snake while still being able to read the display. A scale is good to have because you can weigh your animal to determine the appropriate sized prey, you can track your animals growth, monitor your animals weight if/when they go off feed, and have good records for your vet should that ever be a concern.
Good luck! Once you get things dialed in it gets much easier and you'll have many years with your awesome new animal!