I am currently in the process of blocking the car. I have it blocked down to 320 with a couple of small burn throughs. I am blocking over an existing finish so they have not gone through to bare metal. Should I keep going to the 500 grit and paint or should I put another coat of 2k primer on and keep blocking till there is no burn through? I dont plan to use a sealer coat I’m going to paint base directly on the sanded surface.