I’ve never in 40 years of old cars in this frozen salt mine seen anything like that with less than 6-8 years and more honestly 10+.I get that as I run into them all the time down here. What is unusual is the amount of rust in the short time.
Something went on there definitely . That truck I referred to earlier was10 YO and a plow truck during the high gas price era. You could tell it had plowed and bern parked . It probably never got washed once And sat much of the year. It’ll clean up well enough . Put some primer and paint on it and be happy. A brush is fine for that sort of stuff.