The fastest way to unlock all the disarms is to holster the gun you are
carrying and just disarm everyone you see. Once you disarm the bad guy
you now have his gun. HOLSTER IT!!! Now repeat the process until Slade
earns all of his disarms. It shouldn't take more than 10 min. to unlock
all 5 disarms for all 3 weapons.
When you do a disarm and you will see the title of a new one pop on your
TV (Disarm should be set on random. FYI the shotgun disarms are the
best)