Thats a hard question, but the good news is that you can do what you want and not worry about scrubbing the value of your car. It is a good idea to undercoat the wheel wells like factory to avoid chips there, but in the underneath of your car will be fine especially in West Texas. After spending many days scraping the underneath of the car, I was not about to reapply the dealership undercoating to maybe have to scrape again one day. If you don't mind the splotchy primer meathod, then go for it. I hate it but thats my preference - a completely painted surface.