My single stage metallic has become dull

I bought my Scamp about three years ago, and I'm quite confident that the paint was laid not long before I got my hands on it. The reason I think this is because it was virtually flawless when I first bought it, but around six months later, I started noticing some defects appearing.

The rear quarter seam at the C-post began cracking and bubbling out with body filler, and I noticed random rough patches, along with other random "pinholes" for lack of a better term. To me, it seems the car wasn't prepped correctly and/or the paint wasn't shot properly, but then again I'm not a body guy. I know little - if anything at all - about paint and body work.

I plan to repaint it, but in the meantime, the finish has dulled. From what I've read, and I've come across contradictory info (or opinions), single stage metallic shouldn't be cut and buffed. But what about polishing? Wax? What is the best way to bring back shine and depth on a single stage metallic paint job? How do I correct blemishes?

I think the previous owner was going for the darker B5 blue, since that's what the car was originally.
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