I cannot stand painting wheel wells. In either case, they always look like heck. At the local art store, I saw one of those green templates that have circles, squares and triangles. Real simple. Well, turns out that every wheel I have since done is the size of one of those templates. So, I lay down a piece of masking tape, put the template over it. I use my exacto to scribe the circle inside the template. Remove the template and peel off the tape. It is probably 95-100% the size needed. I place it on the wheel after having painted it silver of white or whatever the undercoat called for. I then paint the tire flat black to my hearts content. Let dry, remove the circular strip of tape and wallah, nice painted tire and wheel well.