Well since no one else is gonna chime in I will. Command Performance is the only way to teach VFR flying because it keeps the student's damn eyes out of the cockpit. I experimented a little bit with this and realized that if on the first couple flights I took a dry erase marker with me and trimmed the airplane for straight and level then had the student put a mark on the windscreen directly between their eyes and the horizon they could target straight and level more aggressively. Then I would stop letting them use it after they started working on slow flight-ish and now I can just say, "CLIMB", "DESCENT" or "STRAIGHT AND LEVEL" and they can go right to it. Now whether or not they can hold it long term is subject to discussion but...
a) That's not my fault and...
b) That's their problem
Another thing...do your student's the favor of utilizing the law of effect by covering up their 6 pack with soap dish covers and let them fly the airplane. Prove to them it's possible to keep an aircraft in level, safe flight without the use of the attitude indicator. Then uncover the altitmeter every now and then and prove that they're on altitude. I sometimes only give my students an altimeter when they're in the pattern...works good. But I digress...as far as the straight and level talking points go...
1) Pitch the aircraft to the approximate sight picture that you had taxiing the aircraft on the ground (works great in the arrow)
2) Set your power to a normal cruise power setting
3) Make small control pressure changes while dividing attention between the relative distance between the dash and the horizon while monitoring change on the altimeter
4) Adjust trim to compensate for any consistent control pressures
5) Divide attention 80% outside and 20% inside (for those of you that USE your instruments) and compensate accordingly outside.
That's the way I do it...otherwise yell, scream, cheat and cry until they find it.