A book I have (Basic Handloading copyright date: 1978) says you should boil the brass in a 'kettle on a range' with detergent.
Boiling spent cases? Wow ... I am glad we got more "modern" alternatives to boiling.
BTW, welcome to the wonderful world of reloading!
As you may read in various threads/posts, there are two camps for case prep: Clean vs polish.
Some reloaders don't care how "shiny" their cases are as long as they are "clean" from fouling from firing (black soot). Some reloaders absolutely must have shiny cases and "polish" them until they have mirror like finish on them.
I am in the "clean" camp, but also like some polish on the case to make sizing easier (Since I use carbide dies without case lube, leftover polish on the brass case acts like case lube).
How fast also depends on how dirty your cases are. My indoor range brass is usually very clean once-fired. I can get spent cases clean with some shine by tumbling them in walnut media for about 20-30 minutes. I usually run several hundred 9/40/45 cases in walnut media with case polish (I used Dillon/MidwayUSA polish and recently switched to NuFinish). If I want even shinier cases, I run them for 1-2 hours.
I have used both walnut and corn cob media. I find that walnut does a better job of cleaning and corn does better polishing. Some reloaders mix walnut and corn. I also tried uncooked rice as cleaning media and it works quite well. I noticed rice does a better job of cleaning after a few batches as it gets dirtier and "rougher".
You can clean your brass in liquid solution, rinse and dry your cases afterwards too - I am sure someone will post the recipe.