It's also possible that they have a quick-don oxygen mask system that snaps into they're helmet with one motion. This is how airline oxygen masks work. They don't have a helmet to snap into, but the oxygen mask hangs within easy reach of each pilot & can be grabbed & put on with one hand in about a second. That way, you don't have to wear the uncomforatable mask all the time, but in a sudden decompression, you can have oxygen on almost immediately.
putting on a quick don mask: