Masking is done with frisket film. It's like contact adhesive, clear so you can trace, but low tack.

This lady on youtube does a great demo



I applied a section of film over the circle areas, and used different sizes lids and cups to trace around cutting the film with a very sharp knife. Remove the section and spray. Fantastic stuff 

On the 2 remaining pops, I painted the 2 black rings as one. I hopefully will be able to overlay the orange ring over the black. Fingers crossed