High build primer will work but its a lot of material. I used one of the layered sandpaper wheels on a grinder to minimize the pitting, then followed it up with a skim of body putty. Prime it good, sand and paint. Gloss black sucks to work with on suspension parts. Use a nice satin black paint and it will always look good. I had mine mixed up at a local paint store and then put into spray bombs.
I used spray on bed liner on the one in my other car. I'm not sure I don't like it better than the painted one.