True Modeler's Rocket Kits NASA Scout Build, Part 12, Nozzle Mask

The instructions say the nozzle and 20/50 ring are painted silver. How do you mask around the ring base?

I found an extra 20/50 ring. Clear Scotch tape was set on my patio door glass. A little more than half the outside ring was traced on the tape with a pen.

TIP: Notice the tape was set on the glass at an angle. This made it easier to cut the curve with a knife.

The two half circles were cut in half.
The curved tape edge was set against the outside of the ring.

After all four pieces were set down the rest was masked off. Even thought the tape mask above the ring looks messy, the seal around the 20/50 ring is clean and tight.

After the tape was pulled the mask was pretty clean. I did do a bit of touch-up with some gloss white and a small brush.