Non specialist threads may also change colour dramatically when varnished, although all threads will change a small amount during varnishing. Ring preparation is important. It can make the difference between a tidy and a messy job. The purpose of preparation is to make sure the rings you have selected have smoothly tapered feet. You cannot whip over a burred foot with a step in it.
Rings leave the factory ready to use, but a little bit of grinding and filing makes the job easier.
Make sure every foot tapers down finely to the blank, that there is no step, and no burrs. Another useful tip, after grinding, use a black marker pen to dull the new shiny surface. A shiny surface will show through any gaps in your whipping a lot more obviously than a black one. Ask the manufacturer for ring spacing. If you want to change this ring spacing, try out your ideas by taping rings in place first with insulation tape.