nitbut wrote:2) shape metal as close as to original shape with hammer and blowtorch
Not blowtorch, unless it's aluminium and then just gentle heat only. You'll need hammer and dolly for that dent.
nitbut wrote:no need to sand, most epoxy primers are not sandable
Incorrect. Most epoxies can be mixed as "sanding" or "non-sanding".
nitbut wrote:build the shape (not sure how I'll be able to rebuild the wheel arch or if there are any special techniques or tricks to perfect that shape,
A stud welder with wavy wire or the loops would be best. Pull with a wire rope ratchet is better than a slide hammer. You need to rebuild the shape of the wheel arch in the metal, not with bog. Probably also need a straight pein hammer and a shrinking hammer to deal with any stretched metal. Access to the back may be limited so you may need to be creative.
nitbut wrote:what would be a good grit range to build the shape?
Start with P40 to P60, then skim and go to P180
nitbut wrote:fill pinholes with primer, sand again to 600 grit
Don't fill pinholes with primer. Use a fine filler or a glaze and finish to P240 before priming.
nitbut wrote:6) add filler primer, sand and feather to 600 grit
7) apply 2k clear coat - sand to 2500 grit
polish car
Clearing over primer is a bit of a waste of time and materials. Once you've blocked out the primer (P240 would be fine) then just give it a sealing coat of epoxy which you can then sand to P400 and which will be smooth enough to put the wrap over.
You're obviously new to body work and probably don't have any of the tools you'll need for this repair including bigger stuff like compressor, DA, stud welder. By the time you buy what you'll need, plus paint, sandpaper, blocks and various other stuff like thinners You'll have spent what you could pay someone to do the PDR, or even have a panel shop beat it out and just finish in primer or epoxy. I encourage people to have a go, but in this case I think you're on the wrong track and if you do it yourself you'll end up with a sub-standard job which will be visible under the wrap.