Question about Wurth SKS
 

CAn this stuff be used over existing undercoating? The PO of my car used rubberized undercoating and I can get most off but not all under the rear quarters? Someone that has the Wurth SKS may be able to check the directions.

SKS is to be used over primed metal at the least according to the instructions. So, no bare metal. I'm of the opinion that it will stick to most CLEAN surfaces. It is a water-borne product (The paint chemists' way of saying water based. It's not, it just cleans up with water). Many water-borne products have acrylic resin as the base and that stuff will stick to almost anything that isn't oily, greasy or has wax or silicone present. My semi educated guess is that it will go over your undercoater and stick.

FYI, I contacted the manufacturer and the response was that the wurth sks can be used over other undercoatings as long as they are not bitumen based. What does that mean?

Bitumen roughly equals tar or asphalt like material; many undercoating systems especially aftermarket ones are bitumen based.