Steel Guitar Builder

Hello my first post here. I'm interested in learning to cast aluminum... specifically endplates for a custom lap steel. Some good videos out there i.e. Myfordguy etc.
Anyone here done castings and in the case of something like an endplate... what is the best way to produce a nice finish on the exterior surfaces?

go to YouTube and type in casting Aluminum, there will be a bunch of videos to learn from....