My big cob went through a stage of just planting and refusing to walk with me in from or back to the field. After trying a variety of things with no joy I bought a pressure halter and have never looked back. In fact, I can now turn him out with just a lead-rope thrown over his neck, no headcollar required! This change in leading behaviour only came about after I used the pressure halter for about 2 weeks. I think usng the halter was kinder than getting frustrated and getting into a tug of war (which I would never win).
Also, given his massive strength, I put it on under his bridle when we hack and always carry a lead-rope in case we have an incident as otherwise I'd have no hope of hanging onto such a big horse in a panic. (Touch wood though as I've never had to use it!)
I highly recommend them (I got mine from the link posted above).
Just remember, don't use it for tying up.