I initially used a flexible pickup tool with a magnet on the end. I pulled piles of rust flakes out. Then I blew compressed air in several times to move the debris to where I could get at it. I also stuck a shop vac hose over openings and then blew in air downstream. Prep work took a lot longer than actually spraying the coating in. Make sure you have plenty of paper or cardboard under the frame when you start to catch drips. As said above, tape off the holes you are not going to use to spray the Eastwood in. I used 2 cans per side and sprayed it in using 2 coats. The key was getting the inside of the frame CLEAN. Wipe up any spills right away. Once it dries I haven't figured out a way to get it off yet. Great product!