Originally Posted By: Bluestream
All valid points, a shop can not spend the time when they need to do volume as it is not cost effective.
My experience with rustproofing started in the 70's with Ziebart. They used a tar like substance that traped water under it and made metal rust faster. They drilled a lot of holes for show. Then a different local place started up and gave new car dealers a big kick-back for each car they sent. Car dealers loved them, and really pushed the sale to people who knew nothing. They used a wax like undcoating that was useless, and went out of business after a while. Again lots of holes drilled. When a hole is drilled bare metal is exposed and it needs to be painted, or grease put on to stop any rust. My Mazda had rust on every hole drilled in it. Worst was that way too many holes were put in just to look good. (My Used 99 Grand AM has holes and they have no rust BTW)
Last guy I dealt with before I started to do my own was good, and would do the job with no holes, or maybe just a few as needed. If you saw him work, you would know what I mean.
You need to add up the economics of appylying this stuff every year. If the warranty requires you to come back every year, and they charge $125 a shot. That's $1,875 over 15 years. A 15 year old vehicle may be worth a $1,000 at best..
Keep in mind the OP was looking for DIY methods of rustproofing. My point in all of my posts is that holes may be needed, but most shops put in more than they need to please a customer, or will drill a hole to save time. (For instance the rocker area can be accessed from below with rubber plugs that the car comes with from the factory.)
IIRC, when my Expedition was done, there were only four holes drilled. Two in the rockers and two to get access to the inner fender at the rear. The rest of it was done using access holes and factory plugs that were already there. This was at Krown.
They pull the tail lights to spray the back part of the rear inner fenders instead of drilling holes.
I have also never seen rust around the holes on vehicles we've had rustproofed, and that has been with Krown and RustCheck, and the Lincoln is 20 years old.