AquiFlux is the best flux available. It is a self-pickling flux, meaning it actually cleans the metal of small contaminants and oils, allowing solder to flow more smoothly and adhere more solidly. AquiFlux is for hard soldering from temperatures up to 1600*, and is perfect for Gold, Silver, and Platinum. Plus, it's water based formula makes for easy cleanup.
I have all and i mean all the fluxes, and tried them all. This is my favorite flux. I reordered a bottle even if I have many of the other fluxes sitting on my shelves.
I learned about this tool at in a class at William Holland, and immediately ordered a set! Perfect for setting and takes away the fear of scratching a stone
I have three of these now because they’re so handy. They are useful to keep small pieces in place when soldering and also many other ways if you’re creative. Highly recommend.