EPOXY COATING
Pouring on the epoxy and using a ply offcut as a squeegee prior to rolling. The molasses coloured epoxy is at least 9 years old, and I've been waiting for a job for it. Epoxy and hardener will keep almost indefinitely if stored in a sealed container away from light, and we had no problems at all with it. The yucky colour was the way it was delivered all those years ago.
Note the patches where we have filled all the temporary screw holes and exposed seams with lightweight filler before sealing the outside.