Mostly I find trimming needs to be hammered home.
Whilst I find that it takes time for students to get to grips with trimming I find it is more a case of making sure they have
done it rather than constantly telling them
how to do it, normally, once they have completed a manoeuvre I ask them if they are happy and then just ask them to take their hands off the controls - they soon realise then the importance of trimming properly.