Great looking project! I have to commend on doing the same thing I did back in 1989 after my first "paid" paint job didn't turn out the way I expected for $600 (family deal..go figure). I know that's not much by todays standards but when you only make $6 an hour that's a bunch of cash. BTW, I did all the finish sanding and taping for that one. I figured, no way I'm paying someone to do this if I can figure it out. And you were right when you said your not worried about the actual painting...thats the easiest part of any paint job....almost like a reward for all the hard work building up to it. Nuke has directed you with some really good tips that I had to learn by trial and error. Especially the one about the primer is only for filling sanding scratches. I would recommend using a long sanding block (I think 8") with some high quality 3m 80 grit
HERE, then 120 and so on, it will allow you to feather the edges easy. There is a reason that the paint stores charge high $$ for supplies. Most of them are worth the extra cash. I have also heard really good things about the newer body fillers. They are supposed to sand better and not bleed through the paint. Anyway, listen to Nuke he (used) to do it everyday. Good luck! I will be following.