Brush /roller.. ok...
Even so when we have brushed onto steel there is more than enough time for it to flow out.
We didnt use por as a finish coat thu. Was used to seal the steel (hot rods/trailer chasis)
Then, Steel panels, hit with automotive hi build.
Blocked back.. any high spots blocked back only so can just see thru the coat NO MORE. The hollows, chips, imperfections where lightly circled with a pencil as one went around with a 400/500mm flexable sanding block.
Fill any chips, even the tiniest of imperfection 2nd coat high build, 1st hit the hollows .. maybe 2X...then whole lot.
Repeat the block down.
If experienced on restored panels.. 2 coats high build, If not 3 coats.
Time to block.. To do a say 69 camaro, full paint, 1st block, about 3 hrs....2nd block 1 1/2 to 2hrs.
Now a thought....every workshop, home garage should have small a compressor .. if looking to the future able to spray up a few panels, couple air tools, blow out the shed, even blow out the car before washing.. look a little larger.. its about air flow, not pressure.
And at least a basic touch up gun (smaller pot, suits smaller compressor to recover between pots)
Bit of capital outlay, but they are part of a list of tools that in the future will occasionally use, yet will be very to glad to have...