I use this and it works great at cleaning up my dirty microfiber towels. I've had some really dirty/greasy ones and it pretty much takes it out with no problems. I sometimes have to use a little more than recommended on the package, but it's great.
Also, be sure you wash your microfiber separate from anything else. That means ONLY wash and dry microfibers by themselves. I also set them for an extra rinse cyle. Do NOT put in with your regular laundry and dry them on med to med-high setting with NO fabric softener sheets. Doing any of the above can and will ruin your microfiber in no time.
I read one story on a car detailing forum where a guy washed his MF towels with his bath towels... Well next time he took a shower he said he felt like he had rubbed wax all over his body. Well in essence he DID wax himself as all of the polish and wax residue from the MF towels transferred to his bath towels. So keep your MF towels separate!