When loaded within the utility category W&B limits, the 172 is so spin resistant as to be entirely useless for spin training. Getting it to enter a spin typically requires much more advanced technique than than recovering IF you can manage to get it to spin in the first place! Entering the maneuver as recommended with power off, and full rudder at the stall break will get it to yaw/roll through the inverted to an upright nose low banked attitude, but it will most often convert to a spiral dive before the first turn is completed.
The spin training required for the issuance of an initial airplane CFI certificate is the only required spin training for FAA certification. The 172 requires some learning and practice just to get it INTO a spin. Getting it out is something the airplane does itself, contrary to your best efforts. By my way of thinking, this is NOT the purpose of spin training! But if one can get a 172 loaded in the utility category to achieve a stabilized spin, then one has certainly demonstrated significant piloting skill!
But this is a kind of negative learning that has the potential to promote complacency regarding the spin resistance of the 172. As noted in an earlier post, the 172 spin characteristics are quite different with an aft CG or with flaps extended. I somehow let a student surprise me once while he was practicing slow flight with flaps. It's a bit of a different animal then. Timely recognition and a smooth recovery is required in order to avoid flap overspeed and/or excessive G loading.
After receiving my signoff for spin training in a 172, I considered it to have been a rather pointless exercise. My previous aerobatic training in the 8KCAB was far more valuable in recognizing and practicing the proper recovery from spins, the supposed purpose of spin training for instructors.
That said, Entering the maneuver a little more briskly and with some power on (>1,500 rpm) will result in a higher likelihood of attaining a stabilized spin in the 172. The adverse yaw added by opposite aileron also helps on the entry, as it's a pro-spin input. An hour's worth of trying to spin the 172 taught both myself and my instructor some lessons about instructing, so there's that. I do wonder how many hours of gyro life we used up that day.
Bottom line: The 172 is not the best choice of airplane type for the purpose of spin training. Stick with something in the aerobatic category.
westhawk