Let’s get this straight. There is no such thing as “nasal resonance”. No matter what you have been told, you will not find any valid, peer-reviewed paper by a qualified scientist that says there is any resonance coming from your nose or your sinus cavities. Sacrilege! No, truth.
If you understand science you will know that you do not deliberately vibrate the bones in your face behind your nose. The sound as it travels may cause some sympathetic resonance in the bones of your skull, but only if you are singing at a loud volume. If you are singing soft jazz or folk music, fuhgeddaboutid. If the bones are vibrating at all it is because you are making a certain kind of sound in the source (vocal folds) and filter (throat and mouth). If you are “singing in your nose” like you had a cold, that’s a different thing and no professional singer wants that sound except as an effect, briefly, for laughs.
Still, the idea that head resonance or nasal resonance is a something persists like a determined mosquito who wants to have you for his dessert. This, like “support from the diaphragm”, is one of those phrases that refuses to die. Even those who claim their approaches are based in “science” sometimes can’t back up what they do with actual published articles. The whole in the mask thing is an OLD idea that needs to die along with all those other silly phrases that make no sense and are more or less useless.
Of course, if you have 200,000 “likes” or “follows” on Facebook or Twitter, that means that everything you say is true, because you have 200,000 hits, right? That also means that if you saw something on TV that says, “Icky Sticky is the best ice cream in the world” that’s true, too, because you saw it on TV!! : /
There’s no business like show business and the show must go on. Before you buy your ticket, investigate the idea of nasal resonance by reading accepted literature in the field. Otherwise, you are drinking the Kool-Aid and remember, that’s not good for you.