It is possible that being drilled about rapid decompression you may resort to EMER DES but even if you didn't as long as the initial action of donning the mask quickly is done the rest is not important and shouldn't raise eyebrows whichever way you do. The difference in EMER DES from normal OP DES is donning mask, extending speed brakes and increasing speed to VMO. At 16000ft. time to useful consciousness is 25mts. and the descent to 10000ft(6000ft) in OP DES it will take less than 3mts. If you extend speed brakes and wind up speed to VMO ALT* should engage in a minute.