Grasping the stabilizer trim wheel will stop stabilizer motion.
I believe this action is only if the stab trim wheel keeps on "coasting" - that is turning slowly under aerodynamic forces if power is removed. Try stopping an electrical runaway stab trim with bare hands and you risk injury.
It seems to me that regardless of the two accidents involving EMCAS the Boeing QRH procedure to counter a runaway stabilizer trim has not changed significantly from back in the days where the 737-200 began operating.
The key is prompt recognition that "something" has caused an un-commanded stab trim operation - whether up or down. The pilot action should be to immediately disconnect electrical power to the stab trim before it moves any further. That is by selecting both stab trim cutout switches to Cutout. Providing there is no delay the stab trim will normally be stopped from moving any further. In turn, operation of the manual trim should be controllable without significant effort.
It is only if the stab trim is allowed to run to its limits (in either direction) because of slow pilot reaction, will the situation become serious. Even then, use of the roller coaster method to relieve aerodynamic forces, is an emergency fall-back technique and assumes the crew are aware of this technique as an essential part of their training. Clearly excessive airspeed needs to be avoided if the roller coaster method is to be successful in regaining manual control of the stabilizer trim position.
The point being made is IMHO Boeing are entitled to assume the crew are technically competent when faced with the instructions contained in the QRH. We know from reading accident reports this is not always true..
It is this writers experience that very few pilots are aware, for example, that rolling the aircraft towards the nearest horizon may be necessary in order to get the nose to drop in event of an extreme nose up wings level unusual attitude. This should be part of training for the PPL and is elementary airmanship. Certainly it should be taught during unusual attitude recoveries as part of instrument flying. It is even described in airline FCTM of some types - including the Boeing series.
The ever increasing accent towards more automation has left basic airmanship in its wake.