If I build a pickup truck and it has one of those beds with the wood and metal runners look, I probably do those different than most people.

My hands are not so steady so painting them is a no go.

Laying down a big decal (which looks great on decal paper) usually doesn't conform well to the bed surface which is molded into the bed - the wood grain and the runners.

So I usually cut out the decal and simply glue it to the bottom of the bed. Meaning I don't dip it on water - I leave it on the backing. (I recommend running a black Sharpie around the edges which will look better to keep any "paper" from possibly showing)

I am sure that is what I did on the Foose truck, as on many other trucks I have built.

On the blue truck I used 1/24 Plastruct diamond plate, cut to size and glued to the bottom of the bed. I sprayed it with chrome paint out of a can.

Plastruct PS 150 Diamond plate. (or sometimes called "double" diamond plate).

I always keep some around for any project - you never know when it will come in handy.