We did a extremely dirty fuselage QB years ago (15?) with a pressure washer. This thing had sat outside for a year and was grungy. After baking in the sun for a few days upside down we scuffed up the primer and reprimed, and painted. Still looks good to this day.
Gary "Seismo" Zilik
Pine Junction, Colorado
RV-6A N99PZ S/N 22993
RV-3B Tail, wings and fuselage.