Kermie - I can concur with the "arm on top of the students seat back" method in the C152. Allows you to get your back into the corner of your own seat and the door which actually moves your torso a good couple of inches outwards. (I used it more to brace myself for a heavy landing than anything else
)
On the touchy feely business, I quite often place my hand on top/bottom of the students throttle hand to demonstrate the throttle adjustments required on the final approach. I've used it on male & female students and have had no problems.
A student shouldn't mis-concieve your intentions if you're "pattering" the exercise, but also dont sit there with your hand/s glued to the students limbs for S&L when not necessary.
S2K
PS I found in the C152 that reaching over to turn off Ignition and masters required arm extension between the students knees! Now that can raise sme eyebrows depending on who you are with!