I have had my PG500 for 3-1/2 years now and live in the Pacific Northwest where temps are somewhat mild. I would continue to play with your LHT & HHT times a bit to try to minimize the "no blazing fire" time in fire pot when the pellet dump caused by HHT time almost smothers the fire. Ideally when smoking you want to always keep the fire going between a nice low fire and a small blazing fire but that is hard to do. When the grille calls for more pellets during the HHT cycle the fire gets a bit overwhelmed (almost smothered) by that larger pellet dump and produces more ash and smoke during that period, and when it finally re-ignites it blows out that ash from it's smoldering time. Typically I run mine at LHT = 35 and HHT = 75, but will occasionally do minor temporary adjust due to hotter summer or colder winter temps. Those times work for my grille, but may not work for yours. I usually do not do long slow smokes on my grille - I do a short smoke (30 mins to 3 hours) followed by a short time on the grille side to finish. That is the true beauty of this cooker as it allows for both smoking and then grilling using the same unit. But I do not think it works really well for long smokes as it does produce some ash and it also burns a lot of pellets (compared to say a FEC100). When I have done ribs for 5-6 hours, there is a little ash all over the cooking grates and I assume a little on the food. Flipping the food over will allow some of the ash to drop/drip off. A pellet grille will produce ash as it is cooking, and the longer the cook the more ash it produces. No way around it. The air flow fan is running at a pretty good speed and will blow this ash around. I have found no way to eliminate it. Yes a seasoned cooker will have "rougher" wall surfaces which will slightly help collect some of the ash but not all. I would not oil the walls. By adjusting the LHT & HHT times to minimize the temp fluctuations and produce a more even flame time, ash production will be minimized. Keeping the fire pot cleaned out will help minimize the ash blow-around during start-up and will minimize the amount of ash in the pot during cooking, but a pellet grille will just produce some ash during cooking. Long post I know, but I hope it helped a bit.