IDEALLY YOU SHOULD NOT DRIVE YOUR CAR FOR AT LEAST 24 HOURS ONCE YOU HAVE FINISHED, SO BEAR THAT IN MIND BEFORE STARTING THIS
Start with the front passenger side wheel. Jack the car up and take the wheel off. The method listed below should be used for each wheel. The instructions that follow are based on two coats of paint which is what I went with as per the instructions on the paint tin, however, some people feel that a single coat is ample.
Clean any excess brake dust and dirt from the caliper using a small hard brush (a wire one is good as it will also help the paint adhere to the surface). You could use specialist cleaning agents such as thinners etc however I just used soapy water and a brush. Dry the area thoroughly. I used an old terry cloth towel and then used another clean one after it. If no muck comes off onto the clean one then you know that the caliper is completely clean and ready to be painted.
Make sure that the area is bone dry or the masking tape won't stick. Be prepared to use a lot of masking tape. Thanks to the curves you will need to rip lots of bits of tape and overlap them so that you can get the area around the caliper fully masked. Take your time here as it will give you a far better job in the long run. You should mask off the pads and the disc. For the curved section in the middle of the caliper you can use the Stanley knife to cut away any excess tape. Just carefully run it around the curved edge and you should be left with that middle area perfectly masked.
On the front wheels I removed the spring clip on the caliper but it's up to you if you want to remove it or paint it. It is very difficult to replace it without scratching the caliper paint so if you do remove the spring clips be prepared to do a little touching up later.
Give the paint a really good stir. Go on for a bit longer than you think is necessary and you'll be good to go. Don't load the brush with too much paint and don't worry if it doesn't cover as thickly as you'd like as you will be going over it again with a second coat later. Take your time and don't use too much paint and you really won't go wrong. Once you are done. LEAVE THE MASKING TAPE IN PLACE and put the wheel back on. Make sure you tighten the nuts and move to the rear passenger side wheel and repeat the steps above. Once you have worked your way around the car, you should have all four wheels back on, all calipers should have had a first coat of paint and all of your masking tape should still be in place.
Have one or go do something else, somewhere else. Wait at least six hours.
Start with the wheel you did first and give the caliper a second coat of paint. Once you are done, carefully peel away the masking tape. Be very careful here. Put the wheel back on and repeat this step with each wheel in the same order as the first coat. If you have used too much paint this step might be a little messy so please take your time. If you have used too much and think that by disturbing the tape you might end up with spots of paint on the disc or the hub etc, my advice would be to leave it in place until the next morning. Or you may prefer to leave it on till the next day anyway.
Now you will have a car with all four wheels on and painted calipers. You're finished for the day. Leave the car alone and go do something else. DON'T DRIVE IT! If you have left the masking tape in place then the wheels will have to come off again tomorrow. If you have removed the tape then you're totally done.