There is a limit to how much thinning you can do, according to the instructions (5% rings a bell).
It was fine for me. I used the high pressure setting on my power washer to clean the frame and blast off scale. I did this twice, the second after hand wire brushing what I could easily reach.
I used marine clean, mixed with water as directed in the spray bottle that came with it, to spray the entire frame. I rinsed with the hose.
The next day I used the spray thing on the prep n ready bottle to spray the whole frame. I let dry, then rinsed with the hose (I think, can't remember now),
Finally, when dry, I brushed the first coat on. I thinned some in advance. Brushed on easily, covered well.
I should have done the second coat when the first was still tacky, but my timing was off and I had to wait for daylight. I took a sanding block and took the gloss off the surfaces I could reach, then brushed the second coat (and did more first coat, since it took less for the second coat so I had stuff to spare).
Simple, but multiple steps with some drying stages (which takes time). I did the work outside, and rolled the truck into a heated garage at night.
I wasn't aware of any smell, but I was outside. I didn't put a drop cloth down for the first coat, so my driveway has spots...I need to recover with sealer in spring anyway, but the drop cloth caught even more the 2nd coat. I didn't wear a tyvek suit the first coat, I did finish marking some jeans and a sweatshirt...both are still very ok as painting clothes or for doing dirty jobs. You can get small amounts off your hands but you must do it with the thinning solvent before the stuff dries, I had no trouble getting some off that came on my wrists between gloves and sweat shirt or tyvek suit arms. Be prompt, my total painting time (each coat) was probably under an hour so the cleanup was quick. Painting upside down with a brush does drip. I was careful because I didn't want to lose any of the expensive stuff, but the drop cloth told the story on the second coat.
Brushing went very well, and I could reach everywhere I wanted. One quart did 2 coats on the frame rear of the cab, with about 4 feet under the cab for one coat. I didn't paint the diff, axle, springs but did do the gas tank plate. With the left over stuff at the end, I did one coat on most of the axle and much of the springs. Since everything was cleaned and treated, I followed up with a black rust enamel on anything missed and the rest of the axle so everything was black. Oh, the inside of my bumper got one por15 coat (this had been scraped, wirebrushed, cleaned, primed, and painted already).
Reg cab longbed.
I didn't expect por15 to be high gloss. I took flat black rust enamel and lightly sprayed the outside of the frame more to take the shine off than to worry about sunlight fading.
It's still a labor of love, but the structural frame repair, cleaning, and por15 treatment ought to extend my frame another 150000 miles easily.