Imagery and simulation can be used effectively in improving technique, particularly when used in conjunction with close study of the technique of high level performers in your sport.
By selecting athletes whose performance you admire in a particular exercise, and either watching or videoing them executing technique, you can build see how they execute every stage of a skill. Using a video recorder you can slow the action down so that the components of the skill can be isolated.
Once you have done this you can practise these components of the skill being observed, and can build them up into a complex action or a good image of the skill as it should be executed.
Alternatively you can video your execution of a skill, and compare your technique as it is with how it should be or how better performers carry it out.