Newton rings are those colored irregular circles you may see when two smooth surfaces are in contact. Film touching glass is the situation most lab workers ask about. The common advice is to use anti-newton ring glass in the negative carrier. Alternate methods: control humidity (to around 40%) — use a spray such as odorless hairspray, use oil carrier, use talc powder.
So, disrupt the surface by making one of them less smooth. That’s the general idea; workable if you are using only one piece of film, however, in a mask stack you will have more than a single piece of film. These two sheets of film may have newton rings if placed back to back, or if one has a smooth emulsion layer. 40 years ago in labs we didn’t see this with Sep Neg type 1 (or 2) and Pan Masking film because Kodak had solved it with design of the emulsion. Now only Kodak Professional Tri-X 320 has the surface tooth; there for retouching — this film isn’t the best solution for masks or separations, alas.
Some possible products, or items to use to cut down on Newton rings. AN glass is available widely. It isn’t rare although reading the forums it seems to be lost and gone.
Some chemicals used in those anti-newton cans of the past: cerium oxide; STAYBELLITE ESTER.
Offset press powder consists of vegetable starch.
Or, try SX 2001 Scannex Anti-Newton spray from: http://www.aztek.com/Products/Aztek%20Imaging%20-%20Scanning%20Supplies(main).htm
There is a patent on using spray to control newton rings which offers some advice along with a description of the problem. https://patents.google.com/patent/US4575398A/en