No, it doesn't hurt the grill. As to your question regarding how long it takes--start to finish quite a while, but your part doesn't last long. I usually do it when I'm smoking... made a batch last weekend so won't need to again for a while but will take some pics next time. I generally use branches (dried hardwood) to keep the size standard (if you mix large and small diameter the small will burn before the big is ready). Wrist size or a bit smaller works for me.... cut in 3 inch lengths, pile them on the Weber (not too big a pile as you'll have to stir them). Split wood would probably work, it's just that branches are handy and I don't have a splitter. What I do is spray them with starter, ignite, try to get them burning uniformly. Restrict the air flow... when the smoke starts to lose color shut the air off altogether. Leave it overnight (don't be tempted to open the lid too soon or they'll reignite.) It's a bit trial and error as when to shut the air down. . . I can pretty much tell from experience, but don't know to explain it. I imagine the type/dryness of the wood and tightness of your air opening effect that... but it works for me. Darned good charcoal. (You need a tight-fitting lid on the Weber, and don't forget to close ALL openings... I made a batch once but forgot to close the bottom vents and had nothing but ashes by morning.)