I'm a huge believer in shadow swinging. I can't always get to the court, but I can always put in some practice in the front yard. True, the neighbors think I'm insane, but it is worth it. They say it takes 2,000 repetitions to ingrain a habit, and you can speed up the process by doing shadow swinging every day when you're not on the court.
I also suggest you do some of your shadow swinging with the aid of a mirror or a camera. I'll set up the camera when working on form and make sure that I'm doing things properly when doing a full power shadow swing. Feedback is good.