
I find it takes a minimum of a week of getting a dog used to a headcollar before you can use it with a lead attached for a walk. I've just done this with my two males, after they had me over on the road lunging after a rabbit on the verge.
After the week of building good associations with their haltis (at first only putting it on, giving treats, then taking it off again, then putting it for treats and meals for a few days, then starting to walk with it on, but the leads still attached to the regular collar as usual) before clipping their leads to it, we're now able to enjoy stress-free walks again, with them walking nicely beside me, and if they
do lunge after rabbits (I must get my friend along with his ferrets) they're checked instantly without me having to move a muscle or even break my stride. :)