I'd have just burnt that off - never going to get it shiny and what's the point for a cheap stove?
This picture was of the end product after I had cleaned it. The point for me, is that I always clean everything I own or borrow before storing or returning it (it’ll often probably be in better condition than when I was given it to use) and I do get satisfaction from doing so. I clean brake dust etc off the alloys on my car to preserve the finish, my boots to preserve the leather(and my feet), wellies, tools I use....an axe, knife, gear must also be maintained, surely, even though they will become dirty again. It’s general maintenance. Having never owned a Stainless Steel stove like this before, I wasn’t aware that the materials would behave in this way through use. Rusting Stainless Steel with carbonised who knows what on it has never been a thing for me to consider before. That’s what lead me to wonder what could be done about it.... which leads me to another question.
How do you clean anything in the field before reusing it? Stabbing a knife into the mud to ‘clean’ it used to be a thing but when I became aware of nematodes etc, I began to wonder if it was still a valid way to do that. In the absence of Soapwort and being mindful of limited water supply...