This sounds like a very helpful exercise. Where on your back is the piriformis located ? If you could tell, it would be very much appreciated.
I wish you well, Eve.
I shall send you the details or the link.As I remember, the sciatica nerve passes through the performs muscle or in someone it can pass by the side of the muscle.
Explanation of the location of piriformis in text form is quite confusing. Pleas Google "location of piriformis muscle". You will get photos which will help you to locate the muscle. By practicing stretching, you may try to feel the stretch in the hip area . This will be more practical way .