on a vertical surface dont thin the paint to much, use just enough thinner so it will flow, you have to stay close so you can pull any runs back into the chip till the paint sets enough so it doesn't want to flow, it helps to have the metal warm, not real hot, just enough so the paint will set faster, take a small piece of metal and put a small ding in it, hang it up and practice filling the dent with paint till you figure out how to do it, better to make a mistake on the metal than on your car, advice is great, but experience is unbeatable, if you have to put 4 or 5 thin coats of paint in the chip that's fine, use the tooth pick to apply the paint to the bottom of the chip and the point of the pick to pull the paint down into the chip and working the paint onto the side of the chip, practice and patience is what creats a good job, keep a lint free rag at hand with some paint thinner on it so if the paint runs out of the chip you can clean it off with the rag, which you probably will do several times, knowledge comes with practice , patience and experience