IMO nothing will work against killing the ticks while they are on there, you've just gotta pull them out! :P have a bucket filled with water next to you so you can just drop them in there as you pick them out.
Hopefully your property doesn't harbour ticks...With my horse, the first place I had him had LOTS of ticks...There were hundreds on him and the sprays didn't keep them off much! He has since moved properties and now, I will only find one tick occasionally on his muzzle or on his leg. I pull them out and squish them between my fingernails.
Poor babies! Hope they are tick free very soon!