While at UTI, we had a paint-mix set up. The list of colors in grams with the smallest amount first goes into the can. Let's say your RED. First, blue, yellow, green, then came red. The can was half full, the rest was the binder resins of choice like acrylic. At this point you have about 50% pigment, but it depends on each color and the amount of pigment in them. So actually, you end up with less than 50% pigment. The resins are activated using a chemical at a ratio to give you 4 hours of pot time, then solvents that control the speed at which the paint dries, but in reality, it evaporates quickly, regularly or slowly. This combination of evaporation, chemical cross-linking leaves the pigment behind. Yes, this professional paint, yet each has it's own amount of pigment that covers black or gray primer. A rattle can work great for you exact repair, because light plays on the pigment and reflect back to you eye in different directions. Yes, we all know this, but how much pigment or solids are in the can.
To conclude, it's the pigment that covers the sealer that was not used, but has to cover primer regardless of color. This is why a good paint booth has good lighting and the cans instruction sheet says spray to achieve coverage. So whether is a $500 spray gun or $12 rattle can, the amount of solids of the pigment used, determine how many coats are required. A quality chemical cross-link acrylic resin cost more than the pigment, but the total amount of actual pigment can increase the total cost of the paint by the gallon or can.
If you have good temperature exposure, many say wait 30 days, then sand the area with 400 grit, pre-clean before & after sanding, tack rag should be hung up to dry out a little before use (Place in a sealed coffee can to reuse later), tape off the re-spray. You're going to have to get pigment on the repair and with good light, stop and look for color match. Use the back-tape trick to roll backward about 3/4" each pass will help eliminate a spray line (Used for clear blending), but use that opportunity to check color match to see if more coats are required until happy. Stop, let it flash, carefully pull the tape back a little more to expose 1500 grit on the OEM clear, then finish with the clear. Just my suggestion.
Note: We had a painter at the dealer, who could match 15 year old dark brown metallic so perfect, you could not tell. I had to ask...he told me that after the color is tack / dust free, I would back the car out into the sunshine and look at it. I could see dark or lighter or match, so if not real close or perfect, I change the distance and direction of the gun for the final application, repeat. Once good, then I would clear it with one light coat at 30% overlap, then let it flash twice a long. This would allow the metal flake to hold their position, then finish it. Worked every time. But with solids, it match, amount of solids and where you start, push it one direction, then move and pull it to you. This eliminates a dry stop but allows the chemical melting to be eliminated.
Best of luck, hope it helps!
