Can the finish be buffed and is waxing recommend?
There would be no reason to buff the coating. The final finish will initially have a mild gloss which may dull slightly over time, but can be maintained by waxing depending on your particular product. Waxing can be done, but normal bedliner is applied with some level of texture to avoid cargo shifting and might not be recommended since the wax might build up in the texture and leave a white film where you could not buff it out properly.
Vehicle exterior coatings (both standard and custom color) are usually a smoother finish than the bedliner product, and can more easily have a wax applied. The custom color or exact match product have a topcoat which is slightly harder than the base coat and contain no powder additive. This product can have waxes applied even more easily if you want the gloss finish.
For black or grey products, we might suggest applying the color coat either in the same color, or clear if you want a high gloss final product.