I find I mostly get creosote at the end of a cook when I let the fire die out, or in the case of my
WSM when I cut the vents to kill the fire at the end of the cook. So you can run a clean fire during the cook and still get some creosote. It's just going happen regardless, the best you can do is slow it down. As far as cleaning, I clean my offset after every cook. There's just going to be
some stuff left behind on the grates but it won't build up bad if you just stay on top of it. Also it never gets hot enough to really cook on there like on a grill.