To be honest Mark, just a cheapy I
had laying around for cleaning off solder joints (I think I got it at a local hardware store in a pack with a nylon and steel, I cut the bristles down on the nylon (to make it a
bit stronger then a toothbrush but softer than brass) and have never used the steel one!). Johnny got the nic-a-brushes that Joe sells and says he likes them quite a
bit.
To be even more honest, I hardly every use it anymore. I find that it runs to big a risk of shining up the high points. If I use a metal brush at all I use my silver one my wife got me for xmas last year. It's a lot finer and less abrasive.
Chris