Brown sugar is white castor sugar with molasses added. In a pinch you can mix your own if you run out while baking. I would not substitute, one for the other though.
Sugar in the raw is a brand name. It is what it implies to be, raw sugar, it also goes by a few other names but is all the same stuff. I wouldn't use it for mixing a batch of Dust. I say this because of raw sugar's extremely course crystal structure. You will not get high enough heat or prolonged moisture to effectively render all those crystals to liquid. Others may say I'm wrong and they have had good results. However I know when I used raw sugar a few times on loins I got a hard candy crust. It was tasty and delicious but NOT what i would want on my ribs.