Congrats on the new pit ! I've put my hands on this unit and it is indeed solid and very heavy. Really needs a counter weight on the door in my opinion.
Anyway.....I own a Horizon and I've never applied high heat spray paint to the main pit, only to the firebox as it did flake in areas. Yours probably will too eventually. What I do is apply vegetable oil to the pit pretty much every time I cook on the unit. Keeps it nice and shiny and looking brand new, kind of like maintaining a cast iron skillet.
My issue out here in the Desert Southwest is the dust storms we have. The dirt loves to stick to an oily pit and I'm really bad about keeping it cover.
Good luck, let us know how this unit cooks and maintains heat as many people have inquired about this unit over the past couple years.
Horizon 24" X 48" Marshal RD Special Offset