Ok, just a little tutorial on block sanding and using guide coat... So the primer is down and dry, and this morning I thought I would run out to the shop for a few minutes before I went to the office and block sand. When you sand there are a few important things you need to keep in mind:
1. ALWAYS use a block (or suitable rigid object for the surface) when sanding. If you don't you run a very high risk of sanding "fingerprints" or grooves into your bodywork. Just because you think that your hand is flat, i can assure you that it isn't. I have been doing this for about 10 years now, and I still don't sand with my bare hand unless absolutely necessary (which is almost never the case). And always use the largest, most rigid block that you can to accomplish the task (please no jokes
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2. ALWAYS use a "guidecoat". A guidecoat is a coat of paint and or graphite like dust that is applied to your filler/primer to help you see surface imperfections while sanding. You can't do a great job without using a guidecoat! Just b/c you can't feel the imperfection doesn't mean it is not there. Now, I can sand a car that is being painted white and get away with no guidecoat... why... b/c white is the most forgiving color to paint a car. It will only show "large" waves or imperfections (large is a relative term). Now I said that I "can" do it, this doesn't mean that I do. I never sand without using a guidecoat. If you are going to use spray paint to lightly spray over the panel, make sure that it is lacquer and not enamel. Lacquer will not clog your sand paper as you sand, enamel has a tendancy to clog especially if you are dry sanding.
3. When you breakthrough to metal while sanding in an area...STOP! This means that the area is higher than the surrounding metal. It would only make the surrounding areas lower to continue sanding so this is your time to move to another location.
Here's a few pics of what a round of sanding looks like...
Here you can see that I have "guidecoated" the entire hood, and started to sand one side of it. When I started the whole hood was uniformly covered in the black guidecoat. I use a dry 3m guidecoat powder that they sell. It is EXPENSIVE, but it's great and worth it to me. It can be sanded wet or dry. In the pic you can see a red spot where I broke through the primer down to the original paint, that's fine. You can also see a few small black marks in the midst of sanded primer. These are low spots that need to be addressed before moving on.
I will show you a closer up photo of a few of these
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