In a 300 the best way of showing a student the airspeed/power/attitude is the following
Hold up your hand so it is horizontal. Hold 4 fingers out. Top of fingers on TPP bottom on horizon. This will give you an approx 50 kt attitude ( I know this is a generalisation but it works )with 18" of power. 3 finger gap and and mp
20" will give you 60kts. 2 finger gap and 22" is 70 kts, 1 finger and 24" will give you 80kts
Although this does depend upon ones height how big ones hands are it does work. It gives students an idea of the attitude to set and the power is easy to set so they only have to concentrate on attitude