I gave up on flitz, never seemed to do much. I dunk all my parks in a tub of blue magic, which is in my experience about 90% as good as mothers (I'll use mothers once I run out, but I agree picking up the blue magic to compare I need to use it up somehow, and I doubt the 10% will matter much for tumbling compared to hand polishing). After even 24 hours most of my screw heads have a nice deep mirror/shiny finish, not brushed looking at all. It can also depend on how many parts you put in though. Too many and they scratch each other and I end up with lots of tiny parallel scratches in my finish. I've got a rotary tumbler though, so maybe it's different

For reference, this is what I get in my small rotary tumbler after 24 hours with a dash of blue magic:IMG_20161105_232320.jpg
(original on right)

It doesn't look quite as good in the picture, but the left one is clean, shiny, and fairly reflective. Looks better than new hardware. Originally these were both from a flooded machine