Without having a real clear picture of your ring-- anytime you have
a precarious soldering, fit it together, and tack-solder one of the
joints. Put solder, and heat it just so that the solder flows enough
that it is bonded with both sides, but don’t flow it all the way,
like you would. Then, go to the side (wherever that is,
depending on the work), and solder it normally, and then work your
way back to the original joint, and re-flow it to finish.
Part 2- The reason you see all those bi-and tri- colored rings with
a satin finish is not just to be trendy - it’s because the texture
brings out the different colors. A high polish on 2-tone can almost
look like one color, again, depending on the work. Satin finish
doesn’t wear very well, but any over-all texture will do the trick.
(You don’t have to buy a satin-finish wheel - jewelers used sandpaper
way before they were invented