1. If you left-click on a county (to open the holdings window in the bottom right of the screen) and then right-click on the picture of one of the baronies in that window, you should be able to auto-generate a character for each barony. (This does not work for the county capital - but, as a nomad, there probably aren't any county capitals.) (However, I'm only about 95% certain that this interaction is available for nomads, because my nomad games usually involve burning everything.)
BUT
2. It'd probably be better for you to completely pillage every holding in all 50 counties. (As long as you can spare the horde troops to put down the inevitable rebellions.)
3. You can hold all of the baronies/temples/etc without penalty: you don't have a "demesne size". No need to do everything right now, if you don't want. (Eg. if pillaging everything all at once would create a clan demand for more land, you could do a bit at a time.)