REGARDING SOMETHING TO DIFFUSE THE HEAT
I have found this to work the best hands down. Get some angle iron (or aluminum) (the large pieces, but does not need to be thick) and cut it and lay it down on a grill grate, pointing up (in normal fashion so it's like an "A" sitting on the grate. We're not lying it on its side or anything). Attach it with bolts and big washers or some other way (by drilling holes through it. They might not come out perfectly straight which is OK, just make sure to get very large washers). Cut and place each piece across the grate to go from edge to edge. (You can optionally not attach it but just lay down these pieces on the grate.) Put that down anywhere over the fire and it will do a fantastic job of evening out the heat. Aluminum is much lighter, but the Iron will retain that heat for a more gradual increase and decrease in temps. The best part is that it allows the meaty goodness to still drip down into the fire which is critical because it really increases some flavoring and extra steaming action of whatever drips down.
NOW FOR SOMETHING CHALLENGING.
I did a smoke last week for a shelter in town, as mostly the whole state was out of power due to the big snow storm we got. I usually use plain charcoal briquettes but this time I had some bags of hardwood lump coals. I love using it for grilling, but wasn't sure about smoking. So I tried it. After 1 hour, I really didn't like the smell coming out of the smoker.. ashtray-like. To avoid the food getting its own ashtray taste, I wrapped the 4 pork butts I was doing (2 smokers) in foil and left it over night. Early the next morning, all the coals had just about gone out, and the temperature was dropping. So I purchased some regular briquettes and saved the rest of the cook until ready. The meat was very tender (all wrapped up) and tasted fine with some brown sugar added, though it had a slight ashtray smell.
So the question.. how would you smoke with the hardwood lump coals? The 2 problems I saw was the nasty smell of it smoldering, and very difficult heat control and length. It was considerably hotter in the beginning, and it all burnt out by the next morning. I frequently do smokes overnight with plain charcoal briquettes without any issues.
And finally, say there is a technique to doing this with hardwood lump coals. Is there a reason to bother with it? I merely HAD them so wanted to use them, but wouldn't buy them for smoking. Definitely for grilling though!