Auto body repair & detailing: Nice sharp clean body lines, rear quarters, leftover paint

Question
I'm doing my first restoration project. I've done a lot of panel replacement floor complete,rear quarters, trunk extensions, and door bottoms. I've primed the entire body with DP90LF epoxy primer and now I am in the process of cleaning things up. This is where you come in. I need your advise on how to proceed from here. Do I scuff the entire vehicle down with a very fine sandpaper. Then apply a high build primer? Any product suggestions? I also would like to know if there is a tip for getting nice crisp clean body lines when block sanding.I read someplace that if you run tape along the crown and use it as a guide. Tried it, not successfully. Any tips on this would be very appreciated.  

Answer
Filler work is something that only experience can teach you. Just keep trying- I do have a product that may help, it's USC Icing, PN 26006 it's a finishing putty, meant to be used for small imperfections and for exactly what you are doing. It's a flow grade putty, levels and spreads nicely, and sands easier than regular filler. Try this trick- when you get the filler where you think it's close- spray some black rattle can paint, fairly lightly, along the line. Then, sand one side of the line. You will be able to see how straight it is by the leftover paint on the opposite side of the line. Neat trick, huh? Once you are satisfied, just sand the rest of the paint off with some 180, and it's ready to go. You can do that over and over  until you are satisfied. That trick, coupled with the icing, should get you through. Primer? Sand the entire body with 320 sandpaper, then primer with high build primer. You are right on the money there. Don't do the whole car at once, the primer will get really textured and gritty. Maybe do 2 or 3 panels at a time. Bill