Three even coats of MP75 were applied, allowing the solvents to flash between coats. The smoother the primer is applied, the more effective it will be in leveling the body surface later when it is block sanded, and less work will be required. We used one grade slower reducer in the primer, which improved the surface finish, but slowed the flash time. After the primer was dry, it was sprayed with a fog of black guidecoat, which is an important aid in sanding. We used black basecoat with extreme reduction, fogged on with high pressure to create our guidecoat, although commercial mixes of specialty guidecoat are available. Do not use a spray can enamel as a guidecoat; it is too coarse of a pattern and will tend to clog the sandpaper, especially if dry-sanding. Even in primer our Vette looked great, a big improvement from the patchwork of body filler we had been staring at. Once the primer is applied and cured, the block sanding process begins.