TLDR: Works like a charm on caked on crud that's set like concrete in your Weber Kettle. See pics !!
I have a Weber 22 inch that basically had a mixture of grease and ash that had set like concrete onto the bowl. I tried everything from oven cleaning fluids to elbow grease with scouring pads and couldn't even make a dent. To make matters worse my one touch cleaning system blades got bent out of shape because of travelling over the caked on residue. At this point I could no longer effectively control temperature. Enter this Lisle 52000 Razor Blade Scraper, I used the plastic blade initially since I was still wary about damaging the finish, this helped remove a decent amount of the residue. However the pesky ones still remained, I switched to the stainless steel blades. Holymoly what a difference !! It started shaving of residue with waaaay less effort, almost like a knife through butter (well really hard butter). The bowl was not shiny before I started, but after taking the scraper to it I could actually see the shiny porcelain coating once more. You can see the bowl and residue that was shaved off with this scraper in the attached pics. My only regret is I should have bought this sooner, this was just using one plastic blade and one steel blade.