My guess is that he will be using Cover Stain as most painters love this stuff since it's fast drying. Problem is that because it's fast drying, it's not a good choice for exteriors since it will get brittle and fail much faster than a medium or long oil primer that dries slower. If he hasn't started yet, I would ask him to use BM's Moorwhite primer. As for an additive, there is no silver bullet you can add, that's what the paint is for. MoorGlo is among the best -two full coats plus the primer should yield years of service.

Thank you so much for your suggestions. I'll double-check the primer and talk to him about the Moorwhite.

If you're out East, FPE is an awesome paint!

NOT cheap, but you're done for a decade with this stuff.

Faron

Should be good for a decade( actually more) using paintguys paint and save yourself a couple or 5 hundred $$$.

Faron, I know you love this stuff but to me( IMHO) it just is not worth the $. I don't think ANY paint is worth that much unless it would double the lifespan, say last for 2 and 1/2 century's