Tr7driver, I also used the Duplicolor kit. It worked well and I like the result. About prepping, I would say read, understand, and follow the instructions to the letter. They include a spray can of cleaner in the kit, but that should be followed up by sanding with a fine grit, and cleaning with detergent like Dawn dish detergent. When the surface is really well dried, you can apply the paint. Like any other paint, it has to be mixed well.
The brush supplied with the kit is OK, but I bought two 1" bristle brushes from my local hardware store. Apply a coat, let it dry for 15-20 min and take a look for missed spots and touch them up or apply another coat. You need good light and rags to cover the rotors and the floor underneath. You'll probably drip some paint, like I did. If you have a good coat on there, let it dry overnight. I did the driver's side calipers on Saturday and the passenger's side on Sunday. All told, it took about 3 hours per side (most of that prep and drying time). And I took time out for lunch.
There's another kit out there, I forget the name. It is also very good, but it is about twice the price of the Duplicolor kit.
Good Luck