It seems that every three days there is a new post for sideskirts.
I know because I've posted a bunch of them. It's a highly complicated issue in that it could be easy to remove the grey off your skirts if you have the right car. However, on the flip side of that, like me and a few others here it can be the most grueling thing you can do to your car even if you do it right.
I followed that post, and this is not to say that castrol business don't work, I'm sure it does, but it ONLY works based on what you got under your grey. And not all e36 are hiding a beautiful paint job under that grey.
BE-CARE-FUL! It seems easy, and it probably is for most people who remove the grey but if you got the wrong car you'll soon be like

and trying to turn back the hands of time. It's costing me a $700 repainting job now!
Plus the bumpers in the front and back (around the tail pipe) are plastic and you'll have to paint over that. The side skirts are metal. Unless someone sold you a half beemer
Good Luck!!