For years, I have stippled the spots on - Take an old round paint brush, cut the bristles off about 1/16 to 1/8 inch above the ferrule (sp???). Dip it in the paint and then procede to wipe the brush on a piece of paper, removing the majority of the paint. Just as you would do when you dry-brush. Hold the brush vertically to the surface where you want the spot located and then jab it against the surface. Do this several times until the spot starts looking like you want it. (Micro brushes work great for this)
This takes practice and if you don't have a paint hulk, you can practice this on white typewriting paper. Just remember you want as little paint on the brush as is possible when you start applying. With practice you will find that it is very easy to very the size and shapes of your blotches.