At work we use lecher black epoxy. Sticks to anything. Parts still needs to be cleaned and prepped properly.
Fairly durable finish. But scratches easily.
For a really durable finish we top coat with glasurit 2k black . Often semigloss or satin.
But just a couple good coats of lechler black epoxy would be more than sufficient for a 4x4. Has a semi gloss finish