Hi, Judy said it well:
Once the joint is completely fused, it is all the same metal. There
is no need to protect the joint during subsequent fusings.
I also agree with Judy about practicing. Practice fusing multiple
times on some scraps before you start working on something larger
that you care about.
Finally, I continue to agree with Judy: solder any time fusing feels
too dangerous. Where that line is varies from person to person,
depending on their skill and confidence. There is no reason that you
ever HAVE TO fuse----it is simply a nice option with Argentium
Silver, to have a really clean joint, with no cleanup. For me, I
generally fuse early in a project. Then, towards the end, when I have
a lot of time and material invested, I am more likely to "play it
safe" and solder rather than fuse.
Best wishes from what has, surprisingly, become "Snow
Country"---I've been snowshoeing nearly every day for the past