Best buffing tricks for oxidized, original paint?

If you use an abrasive "stroke" on a single stage metallic, depending on the grit, you streak the aluminum particles. Whether wet sanding, OR with a circular buffer, you can and probably will "streak" the aluminum.

However, on old metallic finishes, when used with mild compounds (AFTER cleaning with a clay bar to remove imbedded dirt), you can use a "random orbit" buffer like you'd use for waxing......They work much better to protect against streaking the metallic because the effective "strokes" are much SHORTER.....the smaller the "stroke", the more even the final buff will be.

Random orbit used slowly and methodically with light compound will protect it against streaking better than any other method, including hand rubbing......Hand rubbing with a good 'cleaner wax' when you're done is a good option.