BlackLexDog the best thing I've found, which is like a halti but better (in my opinion ) is and Infin8 halter from Black Dog.
I have tried everything else on one of mine with no luck, but put her in one of these and she is feather light. Yay!
It is formed of a martingale style collar with a narrow strap that goes around under their face and back to the collar in a figure 8. It exerts very gentle pressure in just the right places, and doesn't ever interfere with panting.
I got mine at the RSPCA shop, on the recommendation of the behaviouralists there. They also showed me how to put it on which was helpful!
It is so nice to walk a big dog without getting a spaghetti-stretched arm!