I used to use watered down hamerite smooth but was not happy with the brush marks so I just took the calipers off, gave them a clean then a lick of primer and then a lick of satin black areosol (halfrauds)
I did try some high temp paint but that just looked pants so cleaned it off
Here are the pictures of the finished items, they look factory (can still see casting marks etc) and they have not pealed etc.
Spraying is the only way to go if you want the best finish
If you do chip any paint off when refitting the springs, just get fine brush, spray some of the colour into the lid of the spray can and touch it up.
What ever you decide DO NOT paint the springs and pads to match!!!!
+1 on the etech stuff, its brushed on but its kinda like gloss paint in that it levels out the brush marks. Excellent stuff, i got mine from ebay and it comes with brake cleaner as well for less than £20. More than enough paint for about 5 cars worth!