Lots of questions, and I have few answers, but here's some of it:
The vibratory tumblers with dry media clean about twice as fast as the rotary tumbler, according to what I've read, but put it on before you go to bed and rinse it out in the morning and then, so what? I've used the old NRA dishwashing liquid and vinegar formula, simply shaking the brass in it inside a gallon jug. This was before my first Lyman Turbo Tumbler. Lots of brass discoloration, but the loose residue junk came out. My recollection is it consisted of a teaspoon of dishwashing liquid and a half a cup of vinegar in a gallon of water, but someone else may remember otherwise.
Lead residue, primarily from lead compounds in primers, will wind up in any case cleaning media you use, wet or dry. It will tend to concentrate more in the dry materials because they are re-used. I don't know if you get enough lead in one pass of liquid cleaner to have any environmental regulations apply to disposing of it? I doubt it, but if you have a septic system and a well, you might want to think twice about it. Check your local regulations.
As for not spreading lead residue around, just rinse well before drying. Make your last rinse with a little distilled water to collect any tap water mineral residue.
The instructions that came with my .308 and .223 case neck annealing fixtures (Evans Manufacturing LC, (319) 236-3877) say the necks need to get to 700-750°F to fully anneal, and that the case heads must be kept below 400°F to avoid any degree of annealing. However, allow me to warn you that oxidation discoloring will occur easily in the oven. Besides, once you've done a distilled water rinse, you can tumble the wet brass with a terry cloth rag for half an hour to get the loose water out. Then just put them out on a cookie sheet and forget about them for a couple of days while you do something else. It won't matter where you have them then.
If you are in a hurry, boil the cases in distilled water and pull them out with tongs one-at-a-time and give them a sharp shake. The shake will clear the excess water and the retained heat will dry the case fast. Again, some discoloration may occur.
I've seen citric acid used in cleaning solution recommendations before. The old NRA formula had vinegar, as I mentioned earlier. I have no clue whether citric acid poses any threat to the strength of your brass or not? You can buy it in powder form from wine making supply houses.
My own thought would be to buy the Iosso case cleaning solution (
http://www.iosso.com/metal.htm). This is a rapid cleaning acidic dip that is safe for brass. Try throwing a tablespoon or two into your cleaning mix as a slower acting use-once solution. If you are adding detergent, make it a pH neutral one, so it doesn't neutralize the acid. You could try baby shampoo or dishwashing liquid.
Rounded ceramic chips of various sizes and grades are used in Vibradyne machines, and other commercial polishing equipment. Big chips may cause dents in a tumbler. The little guys would be safe in your tumbler and could be mixed with the liquid cleaning solution to help clean brass particles off the ceramic surfaces. Otherwise they will clog and stop working.
Liquid in a tumbler takes more primer residue out of primer pockets than dry media does. It doesn't clog flash holes as dry media will. I don't know of anybody who has found primer residue affecting accuracy in any measurable way. Perhaps someone in the bench rest community can see the difference? I ignore it, so I can't say this is a particularly important advantage, other than there are people whove broken de-capping pins on media stuck in flash holes before, and there is no advantage to joining that club, either.
Nick