XIM is what I have used in the past for steel sign poles its a good product, I don't recall ever using it on wood though. We use fast dry blockout white from Chromatic now. The guys were using something else prior and it was not taking care of the fuzzy surface MDF has especially after routing so I asked them to switch to blockout, the pigment is heavier in this verses what they were using. I'm still against using MDF but its not my decision to make, I'm just concerned we'll have some come back because of water damage.
Mark