I read about using the degreaser and thought it would be time consuming, expensive and messy, so I never attempted to do it that way.
But my skirts were showing the body paint in sufficient areas where it looked like sh#@t. Understand that I don't consider my BMW pristeen, nor do I intend to throw a lot of time and money at a $6500 car with 96000 miles. So with my experience in "wheeling-out" my boat, I decided to try the same approach to the skirts and it worked very well. I used the same gritty compound (auto rub compound should work similarly) that I used on the gelcoat of the boat and was able to wheel off the grey overcoat within 10-15 minutes per side. The edges around the jack ports went down to white (primer or bare plastic?), but nothing a touch-up brush couldn't handle. One section-left side between the rear of the front wheelhouse and the A pillar (door bottom) doesn't look too good, but alot better than the old gray. The local auto paint supply store mixed-up Boston Gruen in a 12 oz. spray can and threw in a can of clear for $35. I will do the jack port covers, the one sh#@iity secton mentioned above and wheel well edges with spray and the worn-through edges around the jack ports with a touch-up brush-voila!
PS. No taping, no gloves and about 2 cents of color restorer compound and 3 cents of electricity. But you do have to have access to a polishing wheel and know how to use it or know someone who does.