My son owns a body shop. I cannot remember the brand name. But any auto body supply will know what you want. Is called a 3 part primer, you get:
1-Primer
2-Reducer
3- Hardner
This stuff is great, with one or two coats and wet sanding between coats with 400 or 500 grit,you are ready to paint.
It fills the blemishes, pin holes,ect.
If he is doing a complete fender or hood that is down to bare metal, he first sprays a light coat of green stuff, I think its etching primer to stop the rust from forming again. Then in a few minutes he sprays the 3-part primer.
Good luck!
Wayne.