Our procedures are;
The cabin crew will grab the nearest drop down mask to where they are. If they are in the aisle, they will either sit on your lap or wedge themselves between the seats until the inital emergency descent is completed. We will normally get a PA from the flight deck announcing inital descent complete. Then we do the monkey swing moving from mask to mask until we reach a portable oxygen set. Once that's fitted, we then go through the cabin assessing aircraft damage and passenger condition before reporting to the senior crew member who feeds all our observations to the flight deck. We only remove our masks once given the OK
by the flight deck. Note - when the masks fall, everyone looks out for themselves, so don't expect a crew member to help you with the mask!
We have one aircraft in our fleet that only has 4 masks on the ABC side. The number of times we've delayed departure because check in have ignored the aircraft config and seated an infant in the DEF side! The drop down oxygen lasts a minimum of 12 minutes and when operated will smell of burning due to the chemical generator.