Elmer ,
I was unlucky enough to find my Truck came ot me with a skim coat to a lot of 25 yr old Bondo pretty much over every body part ,I opted for $$ sake ...since it would kill my budget to let the Body man strip the sheetmetal ...I went to my local Monument place ...yes the TOMBSTONE people , they were expierinced and happy to sand blast all my sheetmetal for a more than reasonaable price .
Just an option to look into , I have found most monument places do all kinds of sandblasting and if they have been around a while they have done Auto sheet metal
