Brazing (hard soldering) pastes

What are the advantages of using brazing pastes that are available from companies such as Fusion? www.fusion-inc.com

[Metalman]

Those look like they are fairly industrial. I checked the alloys they have listed and I was concerned about the metal mix.
So  - you may be able to use those brazing pastes but you will want to check how the alloys line up with the fine jewelry industry in terms of metal mix.
Using a paste solder can be very helpful for locating the solder exactly where you want it. They should work well