When drilling your starter hole, drill from the inside due to the fact that this is a curved surface, and if you should so happen to slip off of your punch mark while drilling, you dont want to damage the finished outer surface of your bucket that everyone is going to see. But when you drill your final hole, drill from the outside so that your drilling burrs will not have to be filed from the outside, I hope that makes sense, its important. Again, drill the starter hole from the inside, and the final hole from the outside.
Use a round file to deburr the hole prior to installing your grommet, this will ensure that the grommet lays nice and flush on the surface of the bucket. Be gentle.