Not much instruction here, just sharing an idea.
Step 1: The Man (or Woman) of Many Faces
Just watch the video (if it's available), look at the pictures and read the notes, and you'll get the idea. I used store-bought masks, but it wouldn't be too hard to make your own. You can make masks that match your face contours exactly, or fit in a specific order. I'm hoping to improve on this idea by adding a nose piece that goes through or under all the masks and lets me breathe in fresh air and not trap the hot air and moisture when I breathe out. Surgical tubing or plain plastic tubes should work, maybe with a molded silicone mini-mask to hold them in place under my nose. I hope to update this in October, and may show how to make your own, especially the black hood with scrim to hide your face.
You can run through all the masks at once, as I do in the video, for a costume contest, or bring a black bag to a party and every so often sneak out for a bit, or go to the bathroom or a closet, and take off one mask, put it in the bag, and return quickly. Note that each mask for "Mr. (or Mrs.) Nobody" shows a different form of being blank. You could use a series of white masks painted in variations of some other theme: clown faces; or skin, muscles, and skull; calm, silly, hysterical, and stark raving mad; human, humanoid, alien, totally bizarre alien; or ... you get the idea.