Hello everyone thanks for taking the time to read this, sorry if there are other threads I looked and did not get my questions fully answered.
I am totally new to painting a vehicle I replaced rear quarters fixed dings and dents and sprayed with 2 coats HOK 3000 primer. Coating came out a little grainy so I then sanded smooth with 400 dry. In some areas there was orange peel I believe it was from original paint , anyway i sanded smooth and went to bare metal in some areas. My 1st question is do i need to re spray entire vehicle, sand with 400 and then apply a seal coat , base, and clear. I used a high build set up. 2nd question is after I either re prime vehicle or spot prime my sand through, is 400 high enough or should I sand with 600 before sealer. Thanks

when you did your first sanding did you use a block and a guide coat?
Jay D.

I did not use a guide coat , but I did block sand everything

Check out the stick posts at the top of this (Body and Paint) forum.

Guide coat is critical if you want it to turn out nice and straight.
Your first round or two of block sanding should be done with coarse grit on a fairly long and hard sanding block. It's the only way to get the panels straight.

Grits are covered in the Sticky Posts as well.

I will check them , thanks