I end up finding someone painted it for me for 85$. I provide a brand new bumper(no need to sand), paint, clear coat, hardner, reducer. I checked his setup (he does this in his garage). You will need a garage almost empty, good air ventalation because it smell like hell. You need to be able to hang the part for painting. The compressor must be at least 4-5HP, it needs to support HVLP spray gun. The general purpose spray gun isn't very useful because of the flow will not be very good, it will affect the paint result. It's better to have spray guns with different tip size like 1.0mm, 1.2-1.4mm, 1.7-1.8mm for different layer like primer, paint, clear coat. Because it's hard to clean after painting each time, so it's better to have different guns for different layers.
Yes. It's better to paint really thin and do many coats.