I've only ever used Kingsford blue bag for DOs. I use the (-)2 / (+)3 method, with compensating for ambient temps, of course, and I adjust based on 70* ambient baseline temp. As for the ashes and temp control, I use tongs to add hot coals, and I tend to push the fresh between the older coals on bottom, sometimes using a side-to-side wiggle motion to slip them in. This seems to keep from driving the ashes in under the oven as much.
I use a propane burner to start my chimney, and if I used, for example, 10 briquettes for bottom heat only, I start another 5-6 briqs at around 20-25 minute intervals, depending on weather conditions, a bit more often with one less briq if some wind is slipping through my kitchen (wind = more oxygen to fire = faster burn rate = hotter oven, thus I use slightly less less fuel). This allows me to add approx. half the fuel required at these intervals to keep more even heat. About the time my coals are half burned up and possibly only generating 50-60% of what I need for heat (the iron holds onto heat well to compensate for burn-down of coals), I have about half of the total I want, and add to what's left of the old...and the cycle continues from there. I never tried to keep the chimney burning continuously, as it would seem to be more difficult to estimate the size of the older briquettes taken from the chimney, thus making it more difficult to achieve the proper amount of heat. If I add a broken briquette, I count it as a half, just for mental notes. Of course, rotate the oven 1/4 turn as indicated.
I use a touchy-feely method for guestimating oven temp to go along with the (-)2 / (+)3 firing method, just as a back-up. For low & slow (~230*) works fine. For roasting/baking temps, it's more difficult for me to judge, as hand distance from the oven is greater to avoid the obvious burn. Everyone's perception of heat on their hand is a bit different, so telling you that at 2" distance from the oven, the palm your hand should become uncomfortably hot is approx. 300* would be somewhat fruitless. The reason I say low and slow is easier to check is I can slip the lid open and see a gentle, slow simmer with slightly viscous mixtures of mostly water, a small percentage of animal/vegetable fats and low to medium-low starch content, and know it should be around 185-190* liquid temp @ 5,000ft where I live...translating to approx 200* or so iron temp. Anyway, there's a few tricks you can learn about temp estimations as well as several other aspects...takes time and a few trips to your favorite DO cooking spot...patience, brother. Baking and roasting are a whole nother story, cuz you don't have free-liquids when baking most items, and with roasting, you may not have enough free-liquids to be able to see it boiling...and it doesn't matter if you're at 250* or 350* iron temp...a rolling boil will still be rolling boil. But in most cases with higher temp cooking, time is mostly what you cook by, with visuals of the dish at some point, maybe a thermo probe check for temp of breads, meats, etc. For pot roast, you might check veggy tenderness as well as the meat.
About half of the ash, for me, seems to stay around the outside edge of the oven, and I pull it back a bit with the tongs as needed. I place my coals in a ring about 3/4 the distance from the center (maybe an inch or less from the edge, almost the same distance as the legs, but a bit farther out), so it seems to be heating the sides about as much as the bottom...too far in and the center of the bottom gets too hot. Ash will accumulate in the center over long cooks, but I haven't had coals go dead. I ran for 6+ hours on my first DO shrimp & sausage corn chowder a while back (a double 12"/6qt DO cook), and the ash was touching the DO in the center, but I had live coals just outside of the ash...that's a pretty long run for a DO dish. Many here say K blue produces a lot of ash, some websites have tested and analyzed different brands, and seem to indicate the same results. I haven't had issues with it for DO cooking. I get relatively slow, predictable and even burn. From first batch, I figure about 30 minutes max before I add more, and then keep progressing from that point, but generally I add within about 5 minutes from the previous elapsed time...sometimes wind may change and make a bit faster burn (hotter as well), so I just keep tabs on what the sizes of old coals are averaging when I add another half-batch.
If further attempts are producing excessive ash and dead coals, you may want to raise the oven and move the coals, at least temporarily, then remove the ash into a metal can (hot, with cinders), then place it all back where you started. The DO won't loose much heat over a minute or two...they're packing plenty of thermal mass. If you have a space large enough (I have a DO table/pan that holds two with some extra space), you could just shuffle the fire and DO once or twice during the cook and remove the free ashes as needed. The minion method may not be catching very well, now I think about it, and especially with a limited head space for the briqs...can't stack 'em partially on top of each other for thermal energy to transfer more easily.
Hope this helps you find that sweet spot.
Eric
