The 744F QRH calls for the partial depressurisation of the aircraft. This is done by a single button on the overhead panel, which automatically raises the cabin to 25,000ft. The problem comes when you have to descend into the more oxygen-rich atmosphere.
On a two man crew with a main deck fire you are going to lose the aircraft unless you can get to a runway within about fifteen minutes. When running 744F command courses we always discussed the option of putting the aircraft onto any available stretch of water if this could not be achieved.
Dave