I bought a couple of them thing you use for washing up, sponge on one side and like a wire wool on the other. I got the caliper paint from halfords (think it was £9) and a decent brush so the hairs didnt fall out.
I cleaned the calipers really really well, then just put the paint on in thin layers allowing for each layer to dry. I bought some new brembo stickers and put them on.
Looking at the calipers closely you would never know they'd been painted, there really smooth. Just make sure you dont put the paint on too think , if it runs theres nothing you can do and it looks awful!
Hope this helps