Tumbler time varies depending upon how dirty the brass is & what media or polishing additive you use. I use both the large & small Dillon tumblers depending upon how much brass i have to tumble along with a small amount of midways additive or dillons.
One thought was to use walnut hull to clean it then tumble it with corncob to polish it.
I only use walnut hull if brass hits the snow in the winter picking up some dirt when it melts down to the ground. Other than that i use corn cob.
Here is a real cheap place to get corn cob with free freight:
When i ordered it from them it had a grainger drop ship invoice in it, maybe their supplier or distributor near me to keep freight costs down???
Weidners also has media at good prices:
Look at the grit sizes on both websites to make sure you get the size you want.