unless its a self levelling paint your using stay away from brushs,takes a lot of skill to leave a perfect finish
Spraying is the best solution ,it will leave the finest of professional finish
Spray in thin layers,many coats as you can ,over 2-3 layers of primer
Your final coats should be cut back using wet and dry [v fine] witth a water lube [wet the paper]
give it a final coat ,then leave the whole thing to cure for at least a week.
Or pay some skilled bloke with 5 grands worth of compressor and gun to do it for you