A turkey baster will fluff it up and get the junk into the water column. You can move a powerhead around aimed under the overhangs or a small pump with a 1/2" vinyl line attached pushes the junk out. If you see any of those plastic back scratchers that look like a small hand on the end at a flea market or dollar store, get a few and heat bend them in various angles. They make a nice sand rake. Several animals also work. Sifting star, goby, and snails.