It is going to be like any paint process. It needs the proper prep done to the item being painted, which means clean. It is also better if the surface could be lightly deglossed or roughed up to provide a good surface to stick to.
Also keep in mind that every product fits a certain purpose, I'm not sure that "Da Dip" was designed to be used in the enviroment of highway driving conditions cruising at speed of 70 MPH plus. Think of it in the manner of a good paint job on a front bumper would cost you a couple of hundred dollars. A can of Dip around $5...there is a reason for the difference in pricing. Just set your expectations accordingly.
"If you have a difficult job to do....Give it to a lazy man....He'll find the easy way to do it."