When I bicycle clean bearing sets for re-greasing, I don’t mess around. I get them to where they look factory shiny; nothing else will do. It doesn’t take long, either. I can have a bearing set out of the bike and cleaned in a matter of three-minutes, maximum.
Shoot them with brake cleaner. Yea, it’s pretty well-known that this stuff works wonders. I have used it for a wide variety of cleaning duties, and it never lets me down. I use this stuff, http://shop.advanceautoparts.com/wcsstore/CVWEB/staticproductimage//N3221/large/7060459_crc_05089_pri_larg.jpg, but there are several other brands on the market that do just as fine a job.
I hold the bearing set in my hand, give it a couple squirts of the brake cleaner, and then vigorously rub them down with a rag, such as an old shirt or sock. If the bearing set is really bad, I’ll do that twice.
Clean with a brass-bristled brush. You know the kind I mean: it looks like a toothbrush, but it has steel, brass, or plastic bristles. Use those. Buy them in bulk. I cannot count the amount of projects they have helped me with. Anyhow, I take one of those and rub any of the remaining caked-up grease off of the bearing set. The reason I use the brass kind is that I do not want to mar the surface of either the bearings or the retainer.
Adjust if necessary. Once they are clean, I make sure that each bearing is sitting in its housing with just enough play. Often times, especially with cheaper bearing sets, the cleaning process alone can close the cages around the ball bearings, preventing free motion. Each ball should be secured in its cage, and yet roll freely. This is learned mostly through trial and error, but it isn’t a real tough concept to understand.
Done! Now, you are ready to re-grease them and get them back in the bike.