when i replaced my floor pan on my 240D i coated the entire underbody, inside of floor, wheel wells, & engine bay w/ a Dupont roll on bed liner.
I got a gallon for like $25 bucks or so... took me a couple hours to do... need to jack up car to be able to reach it... make sure its well vented, or you just don't go near it for a day... lol... i was feelin pretty good by the end of the night... i seriously shook can, grabbed an old towel wadded up & applied.
its got this nice rubberish texture... yet debris doesn't stick...
no chipping/scratching/peeling yet almost a year and a half later... also much quieter inside now
who needs zeibart anywho