This is a bit larger and in reverse route the tourist guides do. Starting in Cabanaconde where you can get by bus from the terminal terrestre in Arequipa. In my opinion it's easier because you go down the steeper part and go up the plainer part (what not means that it isn't steep). Staying the night can be done in San Juan.
You get a plan with bus depatures at the arrival in Cabanaconde. There you have to pay inoffical taxes (as far as I remember 50-80 soles for foreigners).
It's highly recommended to wear trekking shoes and bring enough water (6L per person for two days). The way is hard and water is expensive.