Final Preparation Before Paint

The final stages of preparing a classic car for paint focus on refining the bodywork so the surface is perfectly straight, smooth, and consistent. Even after major bodywork and primer application are complete, careful inspection and correction are essential before color is applied. We join Matt Roehrick of MCA Kustoms in Faribault, MN to explain the process involved in creating a show car finish.

The process usually begins with sanding the primer while using a guide coat. A guide coat is a light, contrasting mist of paint or powder applied over the primed surface. As Roehrick block-sands the primer—often with 320–600 grit sandpaper—the guide coat reveals imperfections. Low spots remain dark because the sandpaper cannot reach them, while high spots sand clean immediately. This visual indicator helps ensure that the surface is level and that body lines remain straight. Sanding is typically done with long, semi-rigid sanding blocks to maintain flat panels and prevent waves in the bodywork.

Once sanding exposes small flaws such as pinholes, minor scratches, or shallow low spots, they are corrected using two-part glazing putty. Unlike traditional air-dry spot putty, modern two-part glazing putty includes a hardener and cures chemically, making it more durable and resistant to shrinking later under paint. Matt mixes a small amount with hardener and spreads a thin layer over the imperfection using a flexible spreader. After curing—usually within minutes—the repair area is sanded smooth with fine sandpaper, feathering the edges into the surrounding primer.

During this process it is common to sand through the primer in certain areas, especially on body lines or edges. Bare metal or body filler must not be left exposed before painting, so these areas are addressed through spot priming. A small amount of primer—often epoxy or high-build primer—is sprayed only on the repaired or sand-through areas. Once the spot primer cures, it is lightly sanded and blended into the surrounding surface so the entire panel maintains a uniform texture.

Before the vehicle moves to the paint booth, Roehrick perform a final inspection under strong lighting and may apply another light guide coat to confirm that all surfaces are perfectly straight. At this stage the body should feel uniformly smooth to the touch, with no visible defects, ensuring the classic car is fully prepared for the color and clear coat that will follow.