Same as Phosphorus32...but I went the dish soap and brush route. Even the modern stuff (my USGI MOLLE pack) says to use mild soap and a brush. (I think laundering/dry cleaning messes with infrared detection, but I digress)
I got a canvas/cotton Chinese chest rig from Sarco that was old, but apparently unissued. I didn't like the looks of some of the white spots on it, and it smelled kind of musty. I threw it in a bucket of really hot water with a few squirts of dish soap, then scrubbed the spots with a plastic brush. Only took a few minutes.
Sun-dried on a deck chair, and it was good to go. Some people stuff the pouches with paper to keep them from shrinking, but I didn't, because I thought it would slow the drying, and I had no problems.
What kind of pouches are you trying to clean up?