So I decided to invest in a paint thickness meter. Delivered overnight via Amazon.

I measured the primer on three panels which I haven't painted yet and it was typically 150-180 um.

I then measured a number of places where I clear coated yesterday and got values between 400-700 um (most were in the mid 400s). Quite a difference there but it also includes the previous basecoat and clear which had been partially sanded down).

So I think my thickness profile looks something like this:

* Epoxy + Primer: 150um
* Base: 30um (a guess)
* First clear coat: 100um (more or less, just a guess)
* Sealer coat: 20um (sprayed very thin)
* 2nd base coat: 30um
* Clear: 150um (sprayed a bit thicker than the first time)

If I'm right, then I would probably hit my second base coat at around 330um. This gave me a number to not go near.

There were three black specks which I cut down by about 80 um or so without making a dent in them. At this point, I was down to about 360-390 um, so I decided to back off rather than risk breaking through the clear. I'm not sure how to handle these. I just tried covering them up with the tiniest bit of base. My hope is that this base will survive color sanding. It won't look exactly the same but they are so tiny (1/32" or less) that nobody will be able to see them if it works.

As for the areas in back where I ran my hose through, those cured overnight into more or less solid masses which sanded off readily (I used 800 grit, taking care to constantly measure the paint thickness but I never got close). They are virtually undetectable now except for a few very tiny needle sized indents.