Since nearly all my bench work is working with small parts and
silver, I can suggest that if you’re using a porous block you
try jewelers’ pins. These are u-shaped two-point pins which are
really great for anchoring pieces in one place. I widen two of
them and place them opposite each other for holding ring shanks
up or down to add bezels, heads, and decorative accents. If you
coat both pieces with flux and line them up where you want them
then gently pass a low flame over from a distance a couple of
times (not enough to heat the metal) the pieces will adhere so
that you can place your solder and come back with a hot flame
and nothing will move. I also use my third hand a lot for those
times when you just can’t get it right.
I bought garnet sand from Rio over a year ago and it’s still
sitting on the shelf - haven’t found an occasion to use it.