Thanks both Lee and Wayne for the input. I've got a fairly expensive rig known for superior atomization, same as used by a professional nearby, and as I mentioned I test for adjustments and spray my final test patch on vertical tin foil, but something always seems to change during the spray. Perhaps the temp of my input air heats up and volatilizes some of the solvent or accelarates some of the curing and voila, the last 1/3 of the spray session is slightly imperfect, often not showing up until 15 min. after I finish. Or, when I mask and re-paint a panel, the step-off is unavoidable. I'm painting at 5000' altitude in the dry, and while adding thinner solves the texture problem, it makes it difficult to avoid accumulation when transiting an edge. At some point I just have to stop sanding and re-painting.
I'm having some good luck sweeping (hardly touching) with 2000 grit, followed by a fine cutting compound (#2) followed by a finishing polish. I also have a slow speed polisher that removes any small scratches left by the paper. The resulting surface still beads water same as the original, but I get a much smoother feel. I'm using Ranthane and it is very flexible, so it takes a lot of focus and attention to blend in a step-off or tape ridge. I've used Imron on the frame; it is great on that, but the flexibility and structural cohesiveness of Ranthane is astounding. If only I could get it to flow with one setting in these conditions.
Wayne - do you recall the 3M compounds you used? Were they machine products applied by hand? I'm not trusting anything yet that isn't mainstream in the professional finishing business. Thanks again.