We have microfiber couches and they are cleanable. The easiest way I have found to do it is to use just a few drops of Dawn dishwashing soap in water and a drill. Seriously! The 4" or 5" white drill brush from this website works great, assuming you have a drill at home it will fit:
http://www.drillbrush.com/soft-white/
You may need a stack of white cloths too to pick up loosened dirt (depending on how dirty the sofa is). I get those at Walmart. Instead of Dawn, a foaming upholstery cleaner would probably work very well with the drill bit too.
Edit: Here are a couple of Youtube videos that show how it works.
https://www.youtube.com/watch?v=yNmCb96uF1g
https://www.youtube.com/watch?v=cVKlObA1QGY