I have an air bulb operated one that is several feet long and is useful in self portraiture but the pressure generated is not enough to release some shutters no matter how hard I stomp on the bulb so I was considering making my own. Would I be right in assuming that basically I can put the two end mechanisms onto a much longer piece of similar-diameter cable? Where does one obtain the cable?

I tried the old fashioned piston mechanism shutter timer but I can't do T or B exposures with it.