I also use a toothpick to fix the small ones. If it is a little larger, I rub the toothpick around on the cement a bit to make the tip bigger. Like mentioned above, you can also get a small paint brush at a craft store. I tried the brush that comes with touch up paint on my wife Escalade, and it looks like sh#t. If I didn't touch the front of my black car up, it would look like white chicken pox.
Scott