I sanded everything by hand. 300 grit wasn’t enough, so I did the whole bumper with 240 grit, then 600 grit, followed by a water wash, degreaser, taping and masking. After that I applied one coat of adhesive primer, then a 1K primer coat, then another 1K primer coat. I wet-sanded with 600 grit, added another 1K primer coat, and wet-sanded again with 600 grit.
Then I made a small mistake — I used too much water and it leaked under the fine line tape, so I ended up with a bit of contamination where I didn’t want it. Since it was my first time doing this, the result isn’t perfect.
After that I applied 3 coats of 1K base paint followed by 3 coats of 2K clear coat. Tip: use strong lighting while spraying, so you don’t overspray or lay it too wet — otherwise you’ll create runs and make the clear coat messy. Another tip: remove the side inserts for the fog lamp area so you get clean edges and lines.
I did the front bumper first, which was a bad choice — I think it’s better to start with the rear bumper because it’s much easier. And one more tip: clean the lines where the fine line tape goes with alcohol as thoroughly as possible, so the tape sticks 100% and you get a clean, sharp paint line.
The bumper pattern structure must go completely OFF
and Adhesive primer is must have 
