First make sure you clean and prime the wood properly. Then use a high quality paint, add paint conditioner (floetrol) and use a 100% nylon brush (like this from Purdy). The bristles are very soft which helps reduce brush marks. The floetrol will help the paint not dry as quickly so your less likely to overwork the paint (i.e. when you brush over paint that's is a little tacky it will leave brush marks). It also helps the paint level.
Good luck!
Good luck!
