Bill,
I have recently ordered from the JAX folks directly, other than a high cost of shipping price was reasonable. I got three products, pewter black , and a brass black and a brass brown. my primary purpose was to blacken brass rod. I am finding mixed results with these. cleaning cannot be overstated. I have used lacquer thinner, Acetone, and used 220 grit sandpaper, and scotchbrite. all of this on K&S products brass. I have found myself re-polishing after the initial blackening, then recoating seams to give the best results. some of this is dependent on the material make up of the base material. have not tried to do brass sheet but you will need to polish heavily to achieve the desired finish, and may not be uniform due to the base material alloy variations.
I would suggest purchasing in pints, while this is a lifetime supply, will help offset the cost of shipping.
Al P.