NJC, I'll share a secret with you; Nu-Finish "The once a year car polish".

On initial treatment I'll put a couple of ounces in the tumbler (but we have a fairly large tumbler) pour it in very slowly while the tumbler is running with no brass. Let it run a few more minutes until the clumps are gone. Then add your brass.

Then I only add a couple of teaspoons about every third tumbler load.

Nu-Finish has no ammonia so it won't make the brass brittle, a bottle of it lasts about four times as long as the stuff you buy from Brownells/Midway, and it keeps the brass from dulling for a surprisingly long time once it is cleaned.

Oh, and it makes the brass look like new gold.