Gout is caused my excess uric acid which crystalises in the extemities - usually big toes, sometimes fingers, rarely knee and elbow joints.
The only home remedy is lots of water, which will dilute the acid and flush out the crystals.
Try and find out the cause, which is usually dietary. For me it's bacon and sausages, but anything spicy should be avoided.
Otherwise, he should see his GP for a course of anti-inflamatory medication which will work a lot faster than the water-flushing, which is the home remedy you asked for.