Step 1: Google it. There might be specifications on the signal for the specific models so you can program universal remotes or something like that.
Step 2: If step 1 brings no results, steal one of the remotes, make sure it works (!), and brown townyze the signal. This would most likely fail if you don't know what youre doing
Step 3: Program your universal remote / rc phone app to send that signal and switch off the projector during a presentation!