I think what Microfunguy is saying is that if the signal sent from the remote control to trigger shooting is too short, the camera will not detect it and so the pulse length will need to be extended somehow. On the other hand, if the signal is long enough there should be no problem as long as the drone outputs between about 3.5V and 5V.
In terms of whether you need to use any more pins, you don't - only the power pins 1 and 5 are used for this purpose.
To set up shooting with remote, go into scripting settings in ALT mode by pressing SET, then Remote Parameters, Enable Remote. There are also settings that determine how the remote operates and are different depending on whether you are using the stable or dev version of CHDK. Alternatively you can use a UBasic or Lua script for more advanced control.