I wanted the staff to open like in the “SG-1 Carter demonstrates the p90” video, but that is all CGI.
On my staff, the bottom half opened fine, opening just enough to reveal the front of the flash. Now I needed the top half to clear the staff barrel.
I made a lever from a wire coat hanger, hinged into the actuator plastic with a screw and a bunch of nuts, washers and locking washers to get the right length and tension. The actuator pushes down, one lever end rides with it, tied with a rubber band to allow for arc. The other lever end pushes the front of the top half up. Good thing it worked because I don't think I could have squeezed anything more into that space. Pictured stretched open for view. 4 AA battery holder cable tied inside for convenience.
I salvaged two momentary switches, one DPTP slide switch, and a small plastic holder from dead desktop computers. I wired them close to the front end so that they are hard to see in the videos.
Here [kmancreeper412] shows off what the five foot staff looks like in daylight.