Your finishing technique has been around for years. It works well, and looks great on your headboard. Just don't doze off during the treatment.
My dad built a camping trailer for us boys (3) when we were teens because the folks couldn't afford to upgrade from the old slip-in, cab-over camper. It was a simple box trailer with bunks built into the side walls and a few racks for gear.
Inside, the plywood walls were given this treatment and it really gave a more rustic feel and also a bit more pleasing aroma than plywood tends to have, at least for a while.
Nice job...
Tim
Jesus still hangs out with fishermen.