1) Type "sv addbot" at the console. You can specify bot names if you want, but it doesn't make a difference. To remove them, use "sv removebot all" or give a specific bot name. They're pretty stupid right now -- based off the ACEBot code. They don't do much besides run around and shoot so far. That will change eventually.
2) PB2 has its own enhanced Q2 client now. It's actually a standalone game -- not quite done, but you can download the alpha builds and they play fine. It should work with other engines, but will lack the paintball2-specific added features that the standalone client has.