I POR'd my frame when they were saying "right over the rust" so i cleaned it up decently and brushed it on.
First winter, i went to powerwash the frame and the stuff came right off (i powerwash my frame every week in the winter time)... from then on, i just put a layer of tremclad on every year....

89 4Runner
3" BL, M/T locks, 33"bfg mt, bilstein, Kayline, tubebumper, toyotafiberglass panels
TBI: Elocker,3.4 w/ORS,b+b,S2Sstg2cams,arias pistons,P+P intake,TRDs/c,URDpullies+7th,downey headers,MAPECU2,WEGO WB, SupraMAF,walboro255,stg4clutch, EPaOo2 sim