I have a Thumblers Tumbler that I used in rock polishing for decades. Even though I have everything to wet tumble and have tried it several times , I prefer dry tumbling with treated walnut shell media.
I just don't care for the water mess and the added step of drying the cases.
If the cases are not 100% dry you can have problems .
Both methods work so it's a just personal choice of how you want to skin that proverbial cat.
Gary