Would not hot water and scraping remove most or all cake? I don't have an overly caked bowl to try myself.
It'd work on soft cake, and I'd bet most really caked up pipes have soft cake.
Hard cake probably requires sanding or thorough reaming.
Most of the cake was pretty soft and easy to get rid of. It was only in the bottom third or so of the bowls that there was another kind of cake beneath, really hard to get rid of. In the course of the earlier thread, i had given up on it, until i got encouraged to scrape out more, and there was still a surprising amount in there. I then did the alcohol & salt again.
Now whats left (or what was, anyways, as i had a few bowls in each, but i guess getting rid of that new cake again would not be a problem) was mainly right on the bottom, and i suspect what really hindered me from removing it completely, was my ability to physically get a good angle for scraping in there.
I tried normal temp water and scraping, too, i will try letting it soak longer, or go for hotter water, or go for the suggested dawn detergent.
I use sand paper wrapped around the base of a Sharpie pen.
Gets right into the base of conical chambers
i tried that, but i always managed to break the sanding paper pretty quickly at the folds on the tip.
I will experiment more, maybe get a different sanding paper etc. I think i was too easily discouraged.