Welcome newbie!
I'll tell you something that took me 3 decades to learn...
1. A closed container with soap & water rolled around about 10 minutes will get the sticky crud off the brass and NOT plug up your POLISHING media.
Soap & water for cleaning, Polishing media for polishing.
Dish washer soap doesn't foam up as much as Dawn, but it often doesn't remove heavy crud like Dawn.
2. When the brass is really corroded/tarnished, or the powder left a really greasy residue, use a little acid.
Something like vinegar or 'Lemi-Shine' works good, but don't go overboard.
3. With crud removed, shake water off, throw directly in the tumbler with dry POLISH media.
Everyone freaks out when I say that, but the very small amount of moisture keeps dust down.
Your brass will POLISH much faster since the crud isn't plugging up the pours in the media.
4. If the dry polish media gets too wet, or too dirty, it's perfectly acceptable to wash it.
Simply dry it in the oven, break up clumps & reuse.
Separating dust can be done effectively by pouring from one container to another outside when there is a gentle breeze, or laying on an old window screen & shaking.
Dust pads the abrasive from the brass and slows down polishing, so when it gets bad I screen the dust out.
I wash brass in a cement mixer, dump out water, flush the brass with clean water, dump again and tumble out the water the brass holds,
Then dump dry media right in the mixer & tumble again for polish, sometimes adding wax.
The brass turns out great, no clumping or sticking in the cases like most will tell you will happen.
Small scale, a gallon can with water tight lid works fine.