I will be taking my car to Krown for the first time, and somebody told me that they drill holes to get to the inside of the panels. My car is a Chevy Cruze if that makes any difference. What are your thoughts on this? Should I get the holes drilled or get it only sprayed underneath? I am very particular about my car, however, I do not want it to rust out. I live in a place with harsh winters and lots of salt on the roads.