I'm buffing the years of built up dirt off a aluminum grain tipper trailer, using a woolen buffing pad mounted on a angle grinder. I'm going in a upwards & downwards motion with great success, however, that's the pattern it's leaving. 1st I thought I'll finish by doing a 2nd, lighter buff or polish in a sideways left/right direction.
But I've remembered advice of cleaning a motorbike frame, to only work in one direction (probably with the frame in the case of a motorbike).
How can I buff and polish aluminum to get the best finish, without leaving a pattern? (Directional buffing/polishing in particular.)