So, for the first time last night, I finally understood the Slurry in my tumbler. My garnets are now underway much better than before!
Now that I have this out of the way, I'm working on just practicing and observing with my tumbling. Another thing to watch out for: the slurry might get too thick (because of A) evaporation or B) as the rocks tumble, rock dust mixed in will thicken the slurry naturally) and the rocks will stop making any progress. And, too much water is bad news because it can end in result to vibratory barrels due to the rocks getting too much action.