Since you have a vinyl pool a lower T/A should not cause you any problems and may help maintain pH better. Besides, pH in the 7.2-7.6 range allows chlorine to be more effective than when it's 7.9. SWCGs do tend to push pH up. Happily, muriatic acid is pretty cheap stuff.

But the way to lower T/A is simply to lower pH. Lower pH to 7.2, but no lower than 7.0. This will lower the T/A a bit (I don't know how much) and then let aeration (ie, splashing, fountains, waterfalls) naturally increase the pH again. Then repeat the process. You "Ratchet" T/A down by lowering pH and aerating to let pH rise again.

So, in answer to your question: Lower pH. The lowering of T/A will follow by itself.