I've had very good results with Dupli-Color Filler Primer from my local Advance Auto Parts store. This is a laquer base, it is sandable and it is made for filling minor scratches and imperfections which makes it perfect for panel lines and rivets on our models. I dry sand using those foam blocks with the grit impregnated on four of the six surfaces in both medium and fine grit. They are available at any Home Depot, Lowes or hardware store.

Al