I've been reading about Pripp's flux for quite a while now, and finally decided to make up a batch, especially for use in kiln annealing (since it's very persistent under heat). Currently I have container that's got the chemicals (3:2:2 by weight ratio of boric acid, TSP, and borax) in water. Some of it's dissolved, and some is still a slurry; I'll add some more water and try heating it again to see if I can dissolve more of it.
Then it goes in a spray bottle, since it's applied by spray to warm metal so that it dries on contact. Should be interesting!
I've tried palladium solder on palladium a few times now, and am not thrilled with the color match (or the softness). Apparently it can't be fused, at least not by a torch, which is unfortunate. I've had recommendations of both 18k palladium white gold solder (hard) and 20-21k white gold solder for use with it; I'm not sure which I'll try for my next project. It's a pair of wedding bands, so I'm hoping for a closer color match, though I did explain to the clients that there would likely be a somewhat visible seam in the back, especially under some lights, and they're OK with that.