Custom Exercises: I have a set of notes for a specialist app that's used by a number of industries. I simply write in the notes words to the effect of "Now do the exercise on the opposite page to reinforce the concept".
The exercise will then be customised for the individual class and inserted in the notes. Usually I use a different coloured page for these. This approach allows the re-use of exercises from a previous class as well as quick replacement if the exercise is not quite right for that class.