A couple of hints. The dry almost sandy looking patches are most often caused by an improper spray pattern. As you spray, it is easy to allow your hand and therefore the spray nozzle to scribe an arc. The result is that the nozzle is closer to the bus as it passes through the arc than it is at the end radius of the arc resulting in more paint reaching the bus mid arc and almost no paint hitting at the end of the arc--except for partially dried over spray which doesn't have the ability to flow out.
Before you do any more spray work try practicing with water sprayed on something flat like a block wall fence. Practice until you have trained your wrist to keep the nozzle at 90 degrees to the surface at all times. You must also train your fingers to use the two stage nature of the spray gun. As you start your pass first open the air valve and momentarily later open the paint valve. As you reach the end of your pass close off the paint flow and just a moment later close off the air fan. The whole process is sort of like a dance and becomes fun once you have practiced enough.
As to what to do with what you have, beware of applying more color--it could lead to paint wrinkle and really make a mess. As long as the color isn't a metallic, light sanding of the dry spots will work as the clears are now all high solids and will "fill" pretty well. Metallic paint doesn't sand well and will require a LONG cure before resanding and repainting. All the same rules apply to clear coat as to application. Clear is less likely to go on dry and is very likely to develop sags and runs if sprayed to heavily--whip up a batch of clear and practice on the side of your neighbors mini van until you get the hang of it.
While you are practicing with water try a few slow motion passes so you can watch the actual application. Always do a small test patch of your mixed paint on a smooth surface (every batch) just to make the gun is properly adjusted.
Jack
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