Just put them in the washer with no detergent. I have heard of people using a little bleach or vinegar but I have no problems with just straight water. Also if you can flip them inside out that helps too.
Treat them like dirty socks,soap, water and bleach and THOROUGH rinse. Thorough rinse, DEFENITELY.
I wouldn't use hot water, and I wouldn't dry them in the drier.
I just turn mine inside out and squeeze 'em under running water. Of course, mine are just paint strainer bags so they might be a whole different animal.
i go to the lake to clean mine. i just scrub them against a rock to get mine clean. i sometimes wait for it to rain and ill just hang them on the window.