Exactly what BPA just said. And also:
Make damn sure they thoroughly understand the certification performance requirements for the different MTOW or speed categories. You do not want them flying Part 23 twins thinking the good engine will always enable them to keep airborne. And even in those that certification requires some positive climb performance, make sure they get to see, more than once, how gear or flap or unfeathered affects performance.
They need to understand when it's appropriate to go straight to feather, or if troubleshooting is an option ie 'fix or feather' decision points.
Understand the difference between certification's limit of 5* angle of bank (for control) to derive Vmc and best performance AoB (2-3*). And when one is more appropriate than the other.