I have been thinking about getting some of the Cycle Design flux for nickel silver. I didn't actually have any problems with the fillet brazing, I just had trouble with getting penetration into the splice. And the big problem was that the only 3/16" tubing I had is really, really thin. Didn't want to use anything that might rust, it sorta defeats the purpose of the stainless.
I polish the stainless tubing on my lathe. Not particularly entertaining, but it wasn't too bad either.