Hey Physiokavs
To activate the stretch reflex without stretching the muscle all you need to do is apply pressure to the muscle and wait until it releases. It is very very important to wait until the muscle has released or you may instigate a spasm if you pull away too soon.
For the psoas and iliacus you must ensure the brain and body is relaxed. Place the patient supine with knees up and feet on the table in order to take the abs out of the picture. This position will also slaken the hipflexors so any "tight" muscle feeling you experience will be the splint. Then gently slid your fingers around the asis and into the muscle belly of the iliacus. Once the muscle is released then move onto psoas. Dig slowly into the belly until you come to the psoas. Apply pressure until hypertonicity no longer exists. Dont stop until you believe the tone has returned to normal. Once done the have them lie on the table until they feel ready to get up. Have them roll onto their side and slowly get them to stand. Dont allow any rapid movement for the first couple of minutes because it may reinstate the splinting.
Feel free to ask questions or come up with a better version. I am always looking to improve my techniques.
Adamo