I just primered my 70' last weeekend and I am
ready to start block sanding it, but am curious what grit of paper to use, and to wet or dry sand everything? Also what is the proper paint to 'fog' on to help get stuff straight? The primer I used is PPG K-36, and I am planning on putting on DP-90 for a while until I actually paint it, how long do I have to spray the DP-90 after final sanding? Thanks for all answers in advance!

First, guide coat with a spray can laquer or even better, the base coat you will use to paint the car. Then, block sand with 400 wet,
re-guide coat and finish with 500 wet. After repairing any "cut-throughs" in th primer you can paint directly on this surface. Do not ruin it with DP sealer. The K36 wil provide much better color "hold out" than DP Epoxy. DP will cause your finish to "die back" and get dull. PPG will give you this same info. So don't waste your money or time re-priming. If you are not going to paint soon after sanding, you can scuff with a gray scuff pad just before you paint