I gravel vac into a bucket, remove the whole filter and place in said bucket. Take out the media compartment and leave the sponges loose in the bucket and place the casing on a towel next to it. Squeeze the media gently in the bucket until the water is cloudy shouldn't take too much. Pour away the bucket of water keeping the sponges in there, then gravel vac again into the bucket, wash the impellor abit check for any snags, then squeeze the sponges again and put every back together and back into the tank. It sounds labourious but its actually quite quick and easy once you do it a couple of times. Make sure you don't be too rough with the media as you can deplete the bacteria if you are also make sure they are always wet with old tank water. You can use a pillow case around the filter if you want to really be anal but a good gravel vacc should eliminate the need.
