For anyone who was wondering about doing this, here's some info as I have just done mine!
What you'll need/What I used:
Heavy Wire Wool
240/400 Grit Sand Paper
Hammerite Rust Metal Primer
High Gloss/High Heat Brake Caliper Paint
High Gloss High Heat Lacquer
Finished result (more photos to come):
OK - so get the car upon axle stands (I did one side of the car at a time) on a nice warm day.
Get the wire wool out and go to town on your calipers. You need to get as much muck/rust off as possible. I used a Rust Metal Primer and it's worth paying for, apart from giving a better finish on rusty surfaces it helps reduce rust better than standard primer, and is worth the extra. Once you have done this, make sure you clean the calipers with some brake dust remover/warm soapy water. Once done, let dry in the sum.
Now I used paint on primer rather than spray, so this meant less masking and covering. Remember to mask up the disc, surrounding areas and any moving parts (especially when spraying)
The primer can said 6 hours drying time, but I found with thin light coat's by the time I had done the other calliper the first was ready for another coat (about 20mins). I put about 4 coats on to get a good smooth finish. Once done I left for 24 hours to harden properly.
Now get the sand paper out (400) and give the calliper a good sand all over. Don't worry about getting it super smooth, decent caliper paint a should help with this.
Once sanded i applied the caliper paint (again using a brush) and found this to be much more controlled than spraying. Again, i did a few thin coats. I suggest getting a good quality paint, preferably a high gloss/high heat enamel. I found that my brush was getting tacky after each caliper as the paint was hardening so fast. This is a good thing, but I white spirited the brush between calipers and coats to ensure I was applying with a decent brush.
The high quality paint gace an awesome finish. If you're going to do it, buy the decent stuff, it looks better and will last longer.
Again, after 2 hours it was pretty much dry, but I left another 24 hours to ensure the paint was solid. Once done use the fine sandpaper to smooth off and matt the paint finish. Not too much sanding, but enough to make it matt and not gloss.
The lacquer I used was a spray on, so I spent time carefully masking and newspapering the surrounding areas. A few thin coats of lacquer and I left everything for about 2 hours to harden before removing masking tape etc.
As you can see, it looks awesome. A few key tips below:
PREPERATION: Dont rush the rust removal, sanding stages, or masking off everything properly. Having a good surface ensures a good finish. And masking off properly means you don't end up with paint on your discs/hoses etc.
PAINT: Spend the money and get good quality primer/paint. The primer i used was excellent and gave a good hard finish, didn't fall apart on sanding, and it also helps reduce the rust building up. As it was also a thicker primer, it gave the slightly rusted calipers a nice smooth finish.
DRYING TIME: Depending on the drying time of your paint/primer/lacquer leave about 20-30 minutes between coats. For good quality paint this is more than enough time. Remember, more thin/light coats are much better than fewer thicker coats. Also, it will dry quicker and smoother without drips or build up. Between stage's leave at least 24 hours (warm/reasonable weather) for the primer/paint to fully harden before applying the next stage.