Thank you for the suggestion, I've been doing that for years.
In fact, I've bought Etch-All from Rings 'n Things for years, even though it's gotten pretty pricey. (Miss you, Russ!)

I do etch when I can't find what I need, but it's smelly and messy time-consuming. Some beads take a few minutes, others take an hour. In the case of the seed beads, it wasn't their matte finish I needed, just the copper finish. And EVERYTHING came off. I think perhaps these were similar the ones ones Birdi mentioned....

Not all beads can be etched. I wanted to matte some small blue apatite beads, and they crumbled. Russ said it was was a reaction to the etching liquid.

Rock tumblers are noisy and take a long time.

Usually matte beads are only nominally more expensive than their shiny counterparts, which is why I snag them when I can.