How to restore rusted equipment.

[hahahadumpling]

I got spit by a acid slime and now my equipment are all rusted. The little fairy helper told me to use grinding stone to get rid off the rust, but I don't know the recipe of the grind stone.
Later I found one grind stone inside a moon gate, but then the grind stone requires polishing powder to use it. How do I get polishing powder?????
Edit: I also got contracted with Ether Disease and now my feet are slowly transforming to hooves. God I'm full of headaches at this moment.

[Leonardo Trapovich]

No idea where polishing powder is, but my solution currently is seeking enchantment scrolls and shrines of armor - 'rusted' qeuipment is '-1' and enchanting does a +1.
As for ether, you will get one antibody in the mail for free the first time, next ones are... tricky - either for small medals from a workshop south of noyel, gambling(A LOT), or wishing at a well(you will probably mutate a lot along the way if you try, but cure for mutation is easier to acquire). Ecopo probably also sells it, but ecopo points are ♥♥♥♥♥♥♥ awfully slow to gain.

[Astasia]

Polishing powder you get by combining junk stone and sulfur in a millstone. It's pretty cheap and will get your gear back up to +0. Save your enchanting scrolls for boosting gear to +2.

Sulfur is found regularly in mountain tiles and doesn't take much effort to mine, basalt pick should do it IIRC.