ijd,i just throw the new lump on top of the old, and sort of mix it around a little bit with the ash tool. but whenever you put in fresh lump, make sure you burn off the VOCs (volatie organic compounds); otherwise, your food will taste bitter and acrid. you'll know when the VOCs are burned off when the smoke turns from white to either blue or clear. usually takes about 15 mintues or so. you do not have to burn off the VOCs with old, used lump, b/c the burn off for that has already happened. this is why i always fill the firebox to the top whenever i put fresh lump in....so that i don't have to wait for the VOCs to burn off for the the next 4 or 5 cooks (depending on what i'm making).
