Re: Upper-arm thinning exercises? DO they exist?
I suspect that any exercise that moves your arms around, like walking or jogging or running, pumping those arms, will help move the lymph around and the wastes out of them. I guess you could also flap about :) I just think about how little I move my arms around sometimes, and yet at other times in my life, I have moved them about a good bit, and my arms have changed throughout my life. Housework, gardening, trimming trees and hedges, etc. Anything that assists the body's ability to move wastes out has got to help you look "toned."
I agree, it's pretty hard to bulk up your arms as a woman. I wouldn't worry about it, I'd just use them. You won't just wake up one morning with bulky arms, you'll see what's happening to them. Take a look at Michelle Obama's arms, too. Dunno if you think those are too muscular for you, but I think they look pretty good.
I like kettlebells for using the body without doing those isolating muscle exercises. Too bad I don't use them more often and practice what I preach, but there are plenty of people who can testify to their power.