Sure thing, the process I used was the indirect method. There are several ways to do this, I chose to do mine on a larger scale. I used a 275 gallon fuel oil tank as the kiln. I cut it in half, lower in the front than the rear (this makes loading the inner barrel easier). After adding angle iron to stiffen the tank, I added hinges, 2 large diameter stacks, and a door to each side to help control the burn. I added a grate to hold the barrel up off the bottom. I used a 55 gal. drum as the retort container. This has to have a removable/resealable lid. This barrel has to be air tight with the exception of a few vent holes, these allow the burnable gasses to escape. I drilled 9 3/8 inch holes in a line down the side of the barrel for the vents. I just guessed at the number required, (I must be lucky because that amount worked perfectly).
To make the charcoal any hardwood will work, I found the pieces that were 4-5 inches long and 3-4 inches across worked the best. Fill the inner barrel loosely then shake to settle and fill to the top,(don't stack the wood tightly it won't all cook). Replace the lid. Fill the kiln as full as possible to where the bottom of the barrel will be. Place the retort barrel with the vent holes toward the bottom. Light the wood in the kiln keep it burning nice and hot, (the hotter the better). Keep adding wood until you see flames coming out of the vent holes. It will sound like a blast furnace inside when this starts. When this starts fill the kiln most of the way up with wood. When the vents stop emitting flame your wood will be charcoal. Let the fire go out it's done. DO NOT OPEN the barrel for any reason, the charcoal is hot enough to burst into flame if any oxygen is introduced. Allow the barrel to cool over night. That's it it's fun and I figure I'll save close to 400.00 dollars not having to buy charcoal.
Plus it starts quicker, burns hotter, and burns more evenly. The first time I used it I was amazed, I filled my chimney starter as full as I could get it. Used 1 double sheet of newspaper, went inside to season the steaks, and pork tenderloin. Went outside and poured the coals into the grill, closed the lid waited for the temp to rise, brushed the grates. I was cooking in less than 15 minutes. After dinner I went out to check the coals, I still had cookable heat 1 hour and 10 minutes after I took off the meat.