The answer for the annual touch up is ...... What ever it takes!
After a year of snow load, acid rain, tree sap, gravel, dirt, dust, moon rocks, bugs of all shapes sizes and stickiness hitting our babies at 60+ MPH, and lord knows what else ... I would go as low as G6 or F7 if needed ... then work my way back up to S.
As for my Caravel
... it is in very good hands and living in the Colorado Rockies
and is a quaint accent piece to a beautiful bed and breakfast. Haven't seen her. (except in my dreams and a few photo reminders)