http://developer.valvesoftware.com/wiki ... n_Tutorial
Should still be the same. I'll give you a sample mission and addoninfo txt file from my small L4D2 sandbox map when I get home so that you're sure to have a correct format.
Just don't forget to put the version number in the name of the campaign :-)
You can also tell them to run it in the readme file or in big fat letters on the L4Dmaps page in Singleplayer first so they don't clog up the game in Multiplayer
Running snd_rebindababasaladaoödnrgfupsxzkx takes a lot of time, but you only have to do it once, and it will work for each playthough. And people don't HAVE to do it... but I can think of at least two maps (Haunts and Jungle) where custom sounds are quite important. Though since I compiled the jungle ruins before The Passing, my sounds might work without the snd_whatever command.
I dunno. People will have to run it once anyway.