ya 40 grit was no typo, like I mentioned my goal was to thin the entire blade, was just for fun as it only to see If I noticed a dramatic improvement in performance. I am in the industry and at the time I was the banq production sous chef, my knives see a regular beating and anything to make the flow through an ingredient easier was more than welcome, I felt like it was a 8hr investment to an 80$ knife to bring its cutting performance up to the 180 $ range.
I haven't had a lot of trouble getting the steel in the fkm range sharp, but it does take some time, it doesn't really benefit from more than 4k in my opinion, but ive put it through some high grit naturals and it likes the polish but doesn't hold on to it,
back to thinning, +1 to what jeff mentioned, just go slow to start and do little by little. as soon as u learn to do it every time you sharpen it will be second nature and u wont need to worry about using a super low grit stone. just what ever one u gonna start sharpening on thin on it first