If it is spray paint, you can prepare the spot as @TwinTurbo suggests, and then mask the area outside the prepared are. Masking tape is used close to the spot, then tape newspaper around the spot and the a couple of feet away from the spot. Tape the paper together so that there is a continuous cover to prevent painting where you don’t want it, with the spot you want to paint in the middle. It is like a sheet the surgeon’s use for operations that covers all the areas but where the make their incision. When you have the areas you don’t want to paint completely covered with enough paper that the paint won’t soak through and mess up the pane beneath, you are ready to spray. Start spraying on the paper about 6 inches away from the blemish and then sweep across the blemish. Go back and forth making sure not to stop on the blemish. Soon, the entire blemish will be covered and you can stop. If you really want to do the job right, use a primer first, but spray on a very thin layer.