I've done many yukons over the years, and here's what I know:
1. Rockers are easy with a long tube - insert at drain holes and apply. There are also body plugs, but they seem to go to the same place as the drain holes.
2. Front fenders use the large openings behind air box, fuse block, etc. A flashlight helps.
3. There are body plugs at the rear behind both tires. You can pop them out and gain access to the wheel wells, not easy though. I believe you can sort of access the front of the rear fenders through the rocker panel.
4. Frame is easy, do inside and out if you can
5. Cover the entire floor pan as well.
6. Doors can be done through the drain holes, or pull off the splash guard and use the push pin holes.
7. Liberally coat all the rear coolant and freon lines, especially the hangers that trap road grime.
I recommend using the conical spary pattern whenever possible as it coats a 360 degree area. Frame and other wide open areas are good with the standard spray, or the 90 degree wand.
Best of luck!
