Learned this the hard way too but from a totally different angle. The glaze doesnt just smell, it insulates the flue so the heat stays in the wrong place and your liner or masonry never gets to dry out right. I pulled a camera on a rental once and the glaze was hiding cracked tiles underneath, so brushing isnt just about smell, its the only way to actually see whats going on in there. If you skip it you cant tell if the crack is new or old and you end up guessing on a job that shouldnt be a guess. Hand brush on a drill is my go to but I break the glaze first with a metal brush head then finish with poly so I dont chew up the liner. Takes longer but you get real eyes on real damage.