IMO, the best 1st step is to flood the wood - off the truck - w/ PENETROL [by Flood, I think]. soak ALL 6 SIDES well, then do a 1st coat of black w/ about 10 - 20% PENETROL added, then 2nd coat straight black - and I use marine enamel.
Try it, Yu'll Like it!

Bill

Moved over to the Passing Lane

"When we tug a single thing in nature we find it attached to the rest of the world" John Muir
"When we tug a single thing on an old truck, we find it falls off" me
Some TF series details & TF heater pics & Rust-a-holics Unanimous parking lot