Weeds,
It took three of us working a 10-hour day to
Color Sand the exterior of my Suburban. We painted with a two-part single-stage urethane enamal (PPG Concept DCC).
As suggested at the link above, we started with 1000 grit and progressed through 1500 and finally 2000 grit. Then, the surface was power-buffed with a buffing compound. The final step (done later) was to polish with a hand glaze (some people used a good carnuba wax).
It takes time and patience but you can get a mirror-like finish.
By the way, if your friends recommended that you start with 2000 grit, they caused you to do a lot of extra work.
Tim