If you are referring to the Mar-K instructions/experiment for applying POR to pine bed-boards, I think they put on 2 coats of POR and then a final coat of quality exterior house paint (Behr, I think). I did that two years ago and so far so good.
We rolled-on the POR, waited until it "tack-up", and then rolled-on the next coat of POR and waited for it to "tack-up", and then rolled on the Behr (semigloss exterior black).
Added later:
We probably applied three coats of POR - we followed what was described on Mar-K's website.
We used short-nap rollers and plastic trays that got thrown away after each coat.
We also used brushes on the edges and seams before rolling on a coat, where possible.
This was on unpainted old wood on a 19+ foot flatbed that had lived in a high desert for most of its life. The under-side of the wood looked like new wood and was not checked. The upper-side of the wood was checked a little. I'll let you know in 10 years how it holds up. I hope to hear from someone else how their paint held up over 10 years.
