I have been playing around with this too.. I use a free editing tool called GIMP, because free/cheap and pass less traveled is how I roll (sometimes not by choice). Anyway I also found that when doing the circles, you can do a drop shadow which will give you a nice glowing affect from the edge, which I have been using on my art. I am learning that it would probably be less time consuming and more accurate to create the button art rather than a layer, since resizing it, PPI, etc all seem to come into play. I am learning a lot, especially with the help of these amazing guys here too.