Having followed your thinking and process for a while now, great pics you sent me BTW, and understand that maybe fairly soon you could get yourself into a situation where you won't have time enough to do everything yourself. Tumbling products can be a very time consuming exercise.
A few years ago, I was looking at setting up a small tumbling process in a factory I was trying to get the processes straightened up in. Eventually, we only installed one vibratory unit, that could be left running almost permanently day and night, it is a very slow process. The rest was sent for outside processing.
To cut a long story short. Search out a business that does it for a living, preferably local. They have the expertise to get whatever finish you require on whatever materials you need to use. I found that they were much cheaper than trying to do processes in house, as they are set up with all the machines and mediums you could ever need, especially where a one man band like yourself is concerned, where eventually, when your business takes off, you won't have the time to do everything yourself.
I know it is good to do it yourself at this time, experimenting and enjoying what you are doing, but in the long run, look to take a bit of the pressure off yourself, as later, your time will become a very important commodity that will be in short supply. Look to get processes into position now, rather than later, so when the time does come, you will know exactly where to go, and can be set up very quickly.