Yes prep work is paramount, paint likes a clean surface
I went with the duplicolor brush-on black myself, did a couple of light coats and then a little thicker third coat. I felt that the brush worked easier and i was able to do it with out taking off the calipers (although the included brush in the kit is terrible/cheap, find a better one.) It's been a couple of years and its holding up well. Plus the black hides brake dust pretty good too. One can is probably good for at least two cars, i did my rear drums as well and still have more than half a can.
I can get a picture up if you'd like to see what it looks like today.