I absolutely echo everything that's been said about teaching in a multi as a new instructor: don't do it. Like USMC, I didn't step foot in a multi as a CFI until I had about 400 dual given in singles. Singles in general are much more forgiving of bad technique than most twins, which allows you to get a good feel for how students react to situations in an easy to fly airplane before moving into something more complex. Students under pressure are known to do dangerous things very quickly, which you as the instructor have to prevent and/or counteract.

Hence why starting in a multi is not a wise idea: you have no idea what to prevent them from doing if you've never been an instructor before. After several hundred hours of dual given in a C172, you'll know exactly where to place your hands during various phases of flight in order to effectively guard the controls. You'll know when to expect them to do funny things like adding flaps above Vfe or "forgetting" to flare. You'll already have a bag of tricks to draw out of.

This all is a positive transfer for when you start teaching in the multi. Guarding controls is the name of the game here, as students can not only hurt you, they can hurt the airplane in a number of ways if you're not doing your part to prevent it. An example would be positioning your foot over the correct rudder pedal before you pull the engine to prevent them from stomping on the wrong one. Another would be keeping your left hand on or very near the throttle quadrant during single engine ops, especially when they're going through a simulated feather or troubleshoot. These are things that are honed as a single engine instructor, and give you a great head start before you start teaching in the twin.