wear safety goggles and use a can or two of brake cleaning fluid and get a few still metal brushes.

It just take elbow grease Simple green is a good idea too.

After painting allow about 24 hours before driving or the brake dust will get embedded in the paint!

Also when applying the paint use a sponge instead of spraying. That way you can dab the paint on (much more control). Just spray the paint into a small container and let it sit for about 30second before applying. This also reduces the drying time and allow you to put the second/third/forth coat on faster. Do about 3 coats min. I did 4 coats. The first coat wont cover much but by 3rd it will be fine.

I painted my GTI VR6 caliper this way and it took me the 1/2day to paint but after 6 years they still look great.