I've never delt with scale rot but there are some home remedies on this forum so would be worth looking for it or starting a thread about home remedies for scale rot. Other than that a vet visit is more than likely needed for some cream or something.
As for misting it's going to vary massively from person to person and what spray bottle you use.
If I had to guess in my 4ft long vivs I mist the substrate 6 times and then mix it and then lightly mist over the top of the substrate again. Probably 10 times in total and that's once every other day because I don't need to boost my humidity much.
With the exo terra viv I started with it would be exactly like above but twice a day or more instead of every other day. . You can't wet aspen much as it will mold so if your going to need to be misting alot then you'll need a different substrate.
While she has scale rot your gonna need to keep her on dry substrate until she is healthy, news paper, paper towel, that sort of thing.
I'm sure there is a tone of information on scale rot on this forum so have a quick search and you'll find everything you need. Or like I said if you can't find anything start a thread on it.
Good Luck