Got any tips for inducing tonic immobility in rabbits?

Also known as trancing. I have tried the suggestions I have read – while on his back, stroking forehead, nose and cheeks and chest. He seems to immobilize for a moment or two, but I’m not sure if it’s true TI because his breathing does not slow – plus he keeps jumping up after I stop stroking. What am I doing wrong? Got any suggestions for doing it right?

Background – I am aware that trancing a rabbit is quite controversial and has been shown to elevate fear in these delicate animals. I would not do it were it not for urgent health reasons. The rabbit in question is a recently acquired rescue German Angora who was previously owned by a 14-year-old who did not care for him properly. Angoras require frequent grooming and clipping, and nothing had been done for him for quite a while. This is a potentially deadly condition for an Angora to remain in for any period of time, since they groom themselves like cats but are unable to vomit hairballs like cats do. This leads to “wool block,” a mass of unpassable wool in the belly, so they think they’re full so they stop eating. He was so covered in mats when I got him it was like a bunny straitjacket – he could not even stretch out his limbs. I have cut away all the fleece on his upper area, tail, neck, and just today managed to get his underside towards his butt end by having a helper hold him sitting up on his rump. But this position does not allow me to clip his chest because the helper’s hands are in the way. Angoras are normally put in TI to do their undersides, but I can’t seem to manage it. Do I just need to wait for him to become more comfortable with me? He’s a very sweet bun and amazingly does not appear to hold a grudge (so far) against me for all this scary stuff I’m putting him through (albeit as gently as possible). I’m new to rabbits, so any advice is helpful.