Ok so finally dove into this the past weekend. Went with Chassis Saver for 2 reasons: great reviews and cheaper than por-15. Brushed it on and I used approx. 1/2 gallon.
Spent all day Sat prepping the frame, all day yesterday painting. Chassis Saver recommends 2 to 3 light coats, with 3 to 6 hours time between coats. Well I started brushing it on at 9:30 in the morning and finally finished the 1st coat at 5:30pm. After a couple of hours and not really feeling like I was getting anywhere, I started applying a much thicker coat. Holy crap did it take forever!!! Did a quick 2nd coating on the rear axle, spring hangers and rear frame that had alot of surface rust, and on the middle section that I'd done a light coat on. Bout 8pm last night I topcoated w/ Rustoleum Semi-Gloss spray can. Took 4 cans of Rustoleum to topcoat entire frame. Letting dry fully and putting the wiring and fuel lines back in tonight.
Didn't take any before pics but will take some finished pics tonight before I put the wheels back on. I'm pretty happy with how it looks, although it took forever and even with wearing rubber gloves, I'm still covered with black paint from my armpits to my finger tips!!
Prep took quite a bit to since Ford put the rubberized coating on the entire frame. I don't think the SD's have this. Scrapped all of it off and all the rusted enamel paint. Then took a wire brush to the hard to get spots and a wire wheel to the rest. Sprayed entire frame with degreaser and washed. Let it sit overnight to dry fully before I painted.
I'm also going to do my fuel tanks, airbag brackets, AirDog mount, and post pump fuel filter mount. Trying to decide if I want to coat the inside of my front and rear bumpers too just to give a little added protection from rusting. Going to get this done within the next couple of days.