[OrrieG]

I did my whole truck with 80 grit and 3m purple shredded wheat pads. You want tooth for the primer to grip to. Etch primer is only designed for bare metal, the data sheets say it is not to be applied over paint or filler. Epoxy primer can go over metal, old prepared paint and filler. I does not need to be a hihg build as it is not supposed to be sanded, just a sealer for primers. Most modern fillers are designed to bond to the epoxy primers so if it is put on right no need to use filler on bare metal. Orge is right about removing scratches, they are easier to deal with than a bunch of low spots that might end up needing a skim coat of filler, or sprayable fillers. Look at doing epoxy then a high build primer like Everclear Uro-fill. Look at these pics on painting my hood. Before then black epoxy primer and you could still see some of the scratches from the 80 grit and body file. Hit it with two coats uro fill and it is as smooth as a babys behind ready for blocking.