Activating the base coat helps in these instances. Generally you can just shoot more clear over the exposed base without any issues.
I had a small sand through on signature car fender except is a bit deeper than most:
View attachment 11409
This was my first attempt at blending paint so I was extremely nervous.
Here are the steps I took:
1. Sand the entire panel where the sand through is with 800 grit until dull.
2. Mask off the rest of the car to prevent over spray from getting on your nice paint leaving only the entire panel you are working on exposed.
3. Now mask off the panel you are working on (this will be removed before clearing and helps keep you focused on the repair area) making sure to leave plenty of room around your sand through for your blend. You don't want to mask too close or you'll leave what they call a tape line.
4. Wipe your panel clean with Wax and Grease Remover. Let this dry while you get ready to spray - 20-30 minutes.
5. I mixed up a small amount of reduced clear to use as in "inter-coat." This is done by using 30 parts clear, 10 parts hardener, 90 parts reducer. (Note: Now I keep SPI intercoat clear on hand for this purpose.)
6. Spray the blend area with the reduced clear using light coats as you would base coat. You want to go past the sand through area with each pass but do not go all the way to your masking tape. Stop a couple of inches short of that
and using your wrist you want to sweep the gun away from the surface. Imagine you are spraying an inside 90 degree corner and you have to turn your wrist to keep from loading the paint into the corner. You will start and stop your passes using your wrist in this manner.
7. Spray a couple of coats of the reduced clear with the second coat extending past the first coat to kind of feather the edge. Remember your base coat will be sprayed on this inter-coat so give yourself some room to work. (Note: the intercoat clear allows you to "see" the true color of the paint surrounding the sand through. This helps greatly in getting a perfect match/blend.)
8. Allow this to flash while you mix your base coat. Mix your base exactly as you did when you first painted the car.
9. No need to sand just begin spraying your base coat very light coats. Make a couple of short passes over just your sand through for good coverage. Make sure to let each coat flash off. By now you will see that things are shaping up and the sand through is pretty much invisible.
10. Make a couple of more passes using the "wrist technique" with each pass going a little farther than the last but not reaching the tape line. Be sure to spray light coats of base until the blend is just the way you want it.
11. Remove the masking from the entire panel where the sand through was and prepare to spray your clear coats over the entire panel.
Hope this helps. I am not an expert by any means but this worked for me and I hope it does for you as well.
The blended repair.
View attachment 11410
Cleared:
View attachment 11411
Buffed:
View attachment 11412