Well DANG! That's the easy way. Leave it to me to find the hard way…I sprayed my mirror with matte clear spray paint
Only problem is, the spray paint doesn't stick if you have to wash the mirror.
The next thing to try is to actually etch the mirror (small mirror, less than two bucks) to see what will happen.
But frosted acrylic on the mirror…how brilliant is that? Wow!