To patina a blade, all you need to do is nothing. Just use it as you normally would. Once in a while clean it off, dry it and lightly oil it. I use motor oil, some people use mineral oil, you could use vegetable oil. The patina helps prevent rust.
Sooner or later, the blade will get darker and develop some stains. If it gets rusty, brush it off and oil it a little more often. The patina is that change in color.
A forced patina is using some type of acid to speed up the process or create a pattern. Cold blue gives a nice consistent finish, mustard works b/c it is mustard seed mixed with vinegar. White vinegar is the strongest, then cider, then wine. Rice wine vinegar is one of the weakest. Something stronger like muratic acid would rust the blade almost instantly and would like etch into the metal in very short order - I would not do this unless I was intentionally trying to etch the blade. (muratic acid is strong and dangerous and paperairplane is not responsible for your chemical burns, blindness, ruined knives, etc)
The reason mustard does not do a lot to BKT's is b/c these are 1095 CV - that little extra vanadium gives you some stain resistance properties. Other carbon steels will rust much easier. D2 rusts less and is almost stainless.
You can also accelerate the process the same as any other chemical reaction - stronger acid, longer application time, add heat, add pressure...
