Mine is set up with an automatic diffuser by means of drip pans between the hanging meat and smoke source; this was the way the Koch smokehouses were built at my dad's store. He had the top chamber to hang meat from, up to 3 rows of metal smoke sticks deep and two rows high. You could hang 325lbs. of slab bacon, two rows deep and two rows high, or 36 hams, 3 rows deep of 6 per row times 2 rows high. The lower chamber door was the oblong iron coal pan that could slide out on angle iron, over a gas straight tube burner that was thermostatically controlled; set the temp and refill the pan every 30-45 minutes. Dad used crushed corn cobs that were easily prevalent, as farmers shelled their corn and left the cob. Dad would pay farmers to truck the shelled cobs to the grist mill to get them ground and bought them cheap in 100 lb. bags we'd store down cellar, usually putting in 60 bags at a time in the crib. Above the burner and coal pan was three drip pans that lifted out, one one each side with another in the middle slightly above; the grease dripping off the upper center pan into the two lower pans, each about 1" deep. Us boys had to clean off the drip pans in between smokes, dumping the grease into a garbage can, along with the aluminum foil we'd cover each with, rinse them off, then cover with fresh aluminum foil and put back in the smoke house for the next smoke. This series of drip pans created a diffusion effect so the smoke drafted upwards evenly, swirling around the meat evenly and then exiting the smokestack. The meat got smoked evenly and the grease was caught effectively, never dripping into the coal pan, and likewise eliminating flareups. The bone rendering company picked up the used grease/foil every week.
My smokehouse design accommodated this concept, albeit a crude imitation, but effective and created enough diffusion to permit good draft of the smoke to evenly smoke the contents and catch the grease too.