You’re talking about the flipbook-function in a material, but there are also flipbook assets which don’t use spritesheets thus support more frames. But I also wouldn’t recommend to use them for longer animations since they’re very demanding in terms of VRAM. I had a 10 second animation in a flipbook and it used 300 MB of VRAM. The movie assets are loading the movies directly from the disc, I guess, what is also demanding in other terms.
I think the best approach for simple animations are particle systems, level sequences or animated materials with something like a “progress”-parameter. You can rebind actors to a new level sequence player also to play multiple instances of the level sequence at the same time.
But in this case I would use a material, yes. You could animate the “progress”-parameter with a level sequence or a curve.
For the mask something like this:
