Agree completely, aluminum just melts away better with HSS in my experience. Some jobs honestly call for the older tools. A good machinist knows to use what works best for the material.

Honestly that timing thing is so key. I'm curious though, how do you actually judge when it's ready for that last pass? Is it mostly by how it looks, or do you go by how it feels under the trowel too? Tbh I've seen guys wait for it to sound a certain way when you drag the steel, but figuring out that exact sweet spot is tough.