DaveT435 -- I hope all goes well with your Surgery this week --
Wow ! 5.5mil = 139.7 microns total thickness - Top
8.0 mil = 203.2 microns total thickness - Rest of vehicle
What I did as a Painter in that field was this --
* Get the vehicle back from the Body shop, with all "repaired areas" filled, and the areas around the repair and the repair itself was scratched to heck with 40-grit paper, files, grinders, etc., because that is how most body men work.. Its a mess..
* I clean it all up with prep-sol, etc., take an air powered D/A sander with some 280 and 360 grit on the pad and smooth out all the scratches as much as possible, blow it all off, clean again.
* Use the DA to feather edge all the painted areas around the repair, so that they are all flat, and exposing all the layers underneath them just right.. Everything needs to be as flat as possible..
* Take the Primer gun, and lay down several coats of primer to completely cover all the area and beyond..
* Take a can of flat black or white lacquer and spray a mist all over the primered areas..
* Use this misted layer as a "guide coat" and a 3m Block and 360 grit wet or dry paper and water, and block sand the entire area so its all scratch-free and flat..
* Tape off the areas around the repair and lay down several coats of paint, last coats adding more clear, last coats more wet so they flash and flow out flat..
* When dry, mist a coat of flat black lacquer on the paint, block wet sand with 600 grit to get it flat again, and try to not embed scratches into the work..
* Compound the area and beyond to include full panels, so it all matches in gloss, and add some meguiars glaze and or wax to protect at the end, after washing the entire vehicle inside and out..
* Inspect the work several times with different eyes, if perfect, deliver to Client..
So, to answer your question, yes, everything from the first work after the repair is to remove repair scratches, get everything flat, then primer it, then block sand it flat, then paint, then block sand it flat, then compound it..
To have consistent total thickness numbers around the car is pretty darn good ! Must have been the Painter with gray hair..

Dan F