Go get something like this. Spray inside the doors, bottom of fenders, inside the bedsides (through the holes inside the wheel wells), and in the rockers, cab corners, and any pockets where there are braces in the boxsides. Get on a creeper and if you see some place where you can spray it in, do it. If you have any questions, please message me with your phone number and i can give you a call. I'm a full time bodyman.
http://www.oreillyauto.com/site/c/detail/TRS1/4423/N0478.oap?ck=Search_N0478_-1_749&pt=N0478&ppt=C0171