Well, I cracked the bone in my forearm a few years back. At first I thought I'd just bruised it bad, or pinched a nerve, but when I got x-rays, it showed a crack. Then I had a cast on for a few weeks, I don't remember exactly how long. For a full break though, I would expect 4-6 weeks. It didn't hurt too much except when I tried to use my hand. I don't know how it would be if the break were further up the arm, but suspect the muscles around the bone would hurt to use while it was broken, and yes, if the cast has been on awhile, the muscle under it never really gets used, so it can atrophy quite a bit. I know this more from each leg at different times. I'd have to hop around on one foot sometimes, so when the cast came off, the muscle development was hugely different from one leg to the other. Ditto the itching as well. You've all that had itch in the middle of your back that you can't reach. Well, this is like that only the itch is almost visible cause you can look at the cast and wish that you scratch under it but be denied. You soon learn how far the fingers of your other hand can reach though.
As for how it felt right after, my wrist just felt like it was buzzing for a couple of hours. 6 hours later most of any pain was gone.
Then on the swelling. It'll puff out a bit, just enough to notice but not huge. and once you don't keep tweaking the swelling will go away in a day or so. They had me wear a wrist guard for a couple of days to make sure the swelling was gone before putting on the cast.
