My 'bulk' tumbling still gets done in a big Dillon CV-2001 tumbler with corn-cob media and Dillon Rapid Polish additive. For some of my 'match' brass though I don't like the fine dust and other associated crap (primer pocket residue, etc. that tends to find its way all over my presses and inside my dies.
I tried one of the small cheapie ultrasonic units with the 480 second (8 minute) timer, heater, and 1/2-3/4 gal (can't recall) tank. As mentioned above, it is pathetically under-powered, only has one transducer right in the middle of the tank, etc. 10-12 cases was the practical limit; more than that and whichever end of the case was 'up' didn't get very clean. Having to continually reset the timer on that unit was a serious annoyance - never noticed a problem with having to let it 'cool down' but then it wasn't putting out *that* much power to begin with.
I then tried wet-tumbling with ceramic media in a Thumler's Tumbler - first the 1/8" ovoid sticks with the angled cut on the end. They clean brass like nobodies business, but with bottlenecked rifle cases - forget it. They have a very bad tendency to pack in there and then get 'locked' until you pry out the 'key' piece that lets the rest of the pieces out. Major PITA factor! I tried some of the very small ceramic spheres (small enough to go through a regular flash hole) but they ended up being too 'clingy' (they'd stick to the case like when you pull something out of a box packed full of packing peanuts) and didn't clean as well. I over-tumbled some brass (>24hrs) in the ceramic media and ended up with some severely rounded over and burred case mouths - to the point I had to trim 5-10 thou off the case neck to get past the burrs. Not good.
I let myself get talked back into trying ultrasonic again - this time I stalked eBay until I found a quality brand-name unit (Branson) with considerably more grunt than the cheapie unit I bought originally. Two transducers (each bigger than the single one on the other unit), a mechanical timer that goes up to 60 minutes (or to continuous), and a pretty serious heater unit. I got the special lid to hold two 600ml beakers, got the thinnest glass lab beakers (so as to not attenuate as much of the us waves in the tank), had one filled with various cleaning acidic solutions (50/50 distilled water/vinegar, Citranox, etc.) and the other with a baking soda/ distilled water mix to neutralize the acid. Now I could do 20-30 cases at a time - yee-haw - and get them all the way clean. Still considerably PITA / fiddle factor involved.
When I read about the stainless steel media at another sight (Sniper's Hide) I was intrigued. I'd read about it other places; Mid Tompkins wrote part of the reloading chapter in Nancy Gallagher's book on Prone and Long Range shooting, and mentioned using steel media to wet tumble with - but what he used was a jeweler's mix that costs more for a pound than five of the wire pins does, so I'd passed. With the low cost of the pins now available, I finally tried the stainless steel media in my Thumler's Tumbler.
Cleaner than US with way less fiddle-farting around with the solutions, rinsing, etc.
Less difficult to separate the media, and less abusive to the brass than ceramic media.
No dust or primer crud on my press or in my dies. (I do decap separately)
Drying isn't too big of a deal. Our oven has a setting for 'pure convection' and I put it in for an hour or two @ 140F. I swear its the most use our oven sees...
If you don't have an oven (or an understanding wife!) just leave the brass neck down in a case tray overnight with a fan blowing on it; should do the trick.
It's certainly not 'necessary' - I just like the cases being neat and clean when I go to load them. If I'm in a hurry though and don't have time to clean as described above, I have no issues with simply twisting the necks in some #0000 steel wool, brushing the insides of the necks and get down to business loading. That works too ;)