u could use a relay as a dry contact 'momentary switch'
If you mean using a timer, you really don't need to do that. If your prop "on" time is say, 10 secs and you don't intend to trigger it again immediately, just add that silent period to your sound file. After you deactivate the prop, the ISD will continue to play out the file and will be ready when you hit the trigger again.When I press the button, the prop will be activated(jump up) and will remain up until I press off. So maybe it would be beneficial to do it the second way....?