Some quick thoughts (as lots of others are in the archives):
- brush or spray, either works just depends on how clean/neat/patient you are...
- prep is the key - I'd advise at least 3 cans of brake cleaner to do the job thoroughly
- If you brush, definitely pick up some smaller brushes from a craft store
- punch out 4 piece of painters tape in a std notebook hole punch. it's the perfect size for the brake pad retaining pin
- painters tape works well as does alum foil (in lieu of newspaper/plastic bags in protecting the rotors, etc.)
- when applying the decals, make sure the paint (spray or brush) has dried at least 24 hours.
- use either soapy water or painters tape to help center/align the decals on the calipers
Good luck and post some pics when finished
Here's the closest I have of my finished product.