Rather than clear powder or automotive clear, I don't do a ton of polishing and buffing but have had fabulous results from Cerakote clear ceramic coatings the last 8 years.
They're liquids, shot with a HVLP gun with a .08 mm tip, and air dry (no heat required). Check out the MC-160 (or MC-5100 especially for aluminum) and hit me up if you have questions. You won't be disappointed.