What grade of sandpaper should I use to rough up the surface of an aluminum passenger car so the "new" paint will adhere? I don't want to use too course of a grit because I don't want to cause groves in the old paint.
The cars I am repainting are the Lionel, MPC, aluminum. I'm using the old paint as the under coat.
I thought of using steel wool, but it has a tendency to leave "shaving" of steel wool behind.
Thanks for any input!