The easiest way is to use friction tape. Friction tape wont stick to any well except to itself. I use contact cement to coat the cowl and friction tape, let them sit for 15 minutes or so to let it "skin over" and then put them together. The nice thing about friction tape is it is very thin and wont be noticed once in place. It is also very cheap and can be found in most hardware stores. Some model A places sell a "special" cowl seal, however I think it is about 1/16" thick which will show after it is installed. I use friction tape on lots of places that might squeak i.e. metal to wood or metal to metal. Hope this helps.