Wow! That’s quite the list! Seems like you’ve done quite a few different variations of frame sealing, coating, painting, inner, outer etc. Any particular reason for all the different methods/variations? Once you’ve done 1 type does a 2nd, 3rd etc really add any additional benefit? I’m in the south and my frame doesn’t have a spec of rust. Everyone who looks at it says it looks like it just came from the showroom floor. Perhaps the PO did some sort of coating? I’m the 2nd owner.
A couple of things, I'm probably a little bit anal about maintenance, and some of my first efforts were done incorrectly or poorly.
Reading any Jeep forum, frame rust is something that needs addressed. My jeep has a solid frame, but had surface rust. The PO/car dealer sprayed undercoating on the exterior prior to my purchase.
I initially addressed the inside of the frame with Eastwood's internal frame coat, but my limited shop space and time had an impact on my results. I bought the Jeep last August, but didn't start any long term maintenance until after the colder weather started. Any work I did, had to be done in one evening, so I could park my wife's car in the garage that night.
About 6 weeks ago, I had access to my garage for longer term repairs. This is when I dropped the gas tank/skid. I decided if I'm going to do the work, do it right. At this time, I drilled additional drain holes in the frame, cleaned the inside with a wire cable attachment in my drill, and washed with degreaser and a pressure washer. I then applied a second coat of Eastwood's internal frame coat. If I would have done this the first time, a second coat would not be necessary.
While I was working under the jeep, I saw some areas that appeared to be covered up with undercoating. Hence the wire wheel, sand blaster, or grinder to remove the undercoating and repaint.
Overall, if I would have done the job in the beginning with the proper tools and procedures, it would have taken a lot less effort. If my frame looked "showroom new", I probably would have only sprayed the undercarriage with fluid film for protection. With a spray gun, this is a 15 minute job.
Tonight, all my efforts seemed to have paid off. I took the top off and went for a ride. To celebrate our first topless ride, my wife and I picked up another couple and drove to a local restaurant. While eating, the restaurant owner/bar tender asked "who owns the blue jeep?" I raised my hand. He said he wants it, and offered to trade his Harley and cash. His wife took a selfie with my jeep. After all my efforts, I finally understand the meaning of "It's a Jeep Thing".