Most people use the top flite panel line pen (or a marker from target for 1/2 the cost). That probably works about as good as anything on film covering. But, I am sure those with more film experience will chime in.....I had bought a MiG-3 from a guy that used monokote, dulled it with steel wool and then used pencil and graphite powder to make panel lines and weather. Fooled many a people into thinking it was glassed and painted.