This quick repair needs some...
This quick repair needs some filler. The area is quickly stripped with a 3M Clean and Strip wheel and then feathered with a D/A.
Metalics get the metallic effect from small particles in the paint. Sanding can disturb the metallic particles in a visible pattern, and it won't readily buff out. Dark metalics are more sensitive than light ones to this phenomena. If the paint is burned out with oxidation, there may be no other alternative than to try an area and see if it will sand and buff out uniformly. Using the finest paper available reduces the chances of streaking the metallic in the sanding process.
None of the original factory musclecar paint jobs were clearcoated, but for a number of years now, clearcoating has become routine. Clearcoats cut-and-buff well, but if the clear is cut-through and the paint is exposed, the hole will be visible a mile away. Even respraying clear over the cut-through won't hide it, since the underlying basecoat will always shift color when disturbed. Our 'Cuda was painted in a solid color without clear.
No matter which type of paint surface is being worked, sand only enough to remove the oxidation and surface flaws, and leave a uniformly de-glossed surface. Don't chase deep imperfections with concentrated sanding in one area, but take a uniform cut over the entire surface. It's difficult to tell if you've gone far enough when the surface is wet (unless you're working in bright sunlight), but wiping the area dry shows the remaining flaws and shiny areas that need more sanding. The paint revival on this 'Cuda began with a cut using 1500-grit paper. Sanding serves as the first step in the buff job and provides an ideal surface for paint adherence. The heavy oxidation is clearly visible, even wet, so it's easy to tell from the distinct color change when the surface is sanded sufficiently.
It's basic, but filler mixes...
It's basic, but filler mixes with hardener, taking a few minutes to cure. To keep the filler clean, never double-dip the stirring stick into the fresh filler, mix on a clean surface, and apply it with a spotlessly clean squeegee with a nice edge.
Touch-ups can range from dabbing in some paint from those little car dealer's bottles to blending-in a repaired panel. In most cases a repair is just that, a fix, and perfection isn't always possible, though certain colors are easier than others. Solids such as the red on this 'Cuda are easier than metalics, and dark metalics can be nearly impossible. The paint should be the same type as that being repaired, preferably the same batch that was used in the first place. Barring using the same paint, take a sample of the original color to the paint jobber and have the paint-match verified at the time of purchase and the tint adjusted if required. Formula tints won't typically be a perfect match. If the paint doesn't match, the repair will stand out.
Achieving a perfect blend into a panel is much tougher than painting a panel section to a character line. Lines or panel gaps break the surface plane to the eye, making it difficult to perceive subtle variations in the paint. With difficult metalics, cutting-in to a line is probably the best way to hide the repair. To paint to a line, back-mask-rather than laying the tape flat to the edge-so it's folded back in the middle at the line, giving it a soft edge.
For very small chips, a paint-brush dab is probably the best quick repair, but not a perfect one. For the best result, try to fill the hole with multiple applications until it's even with the surface. Avoid building up a ridge of paint outside the hole. After filling, the spot can be color sanded and buffed. Larger flaws like surface gouges or large chips can be filled with spot putty. Traditionally, these are quick-drying nitrocellulose (lacquer) products. Spot putty shrinks slightly and cannot be effectively used in thick layers, since drying time goes up exponentially as thickness increases. Catalyzed spot putties are available, but the grain generally is not as fine as the nitrocellulose formulas, and if you have many small repairs, constantly mixing fresh batches slows progress. Fill ever-so-slightly higher than the surface of the chip or gouge. Don't cake the putty on or it will be impossible to sand it level without sanding through the adjacent paint and distorting the paint's surface.
You're not slopping plaster,...
You're not slopping plaster, so apply the filler as smoothly as possible and don't over-work the material.
Once cured, the filler is...
Once cured, the filler is sanded level. We used 80 grit on a short hard board. It can also be filed with a Surform file to rough it, but on a small repair like this it isn't necessary if it's applied nicely.
Next the area is glazed with...
Next the area is glazed with spot putty to fill the sanding scratches and minor surface imperfections. We used the same nitrocellulose spot putty used to fill the chips. The key is an even, thin coat using as few passes as practical. Overwork the spot putty and it will wad up.