Sorry posting as I think of things.
I recommend that you start Harley on a gentle leader or I prefer a halti and martingale or harness setup.
Halti goes on and a line is run from it to a harness or martingale to protect against the him getting away if the halti comes off.
Martingale is what many use on Greyhounds and tiny ones can be found with out a lead attached all ready.
I run my girl on the halti harness and had one custom made with a D ring in the front to attach the halti.
Haltie needs to adjusted so that it is tight in the back and pined or stitched so it will not slip.
Halti works well in a situation that you must get a dogs mouth closed and fast. Gentle leader does not have that ability but works well for control.
Hatli is not a muzzle and it is not unkind.
http://www.sitstay.com/store/equip/collars2.shtml http://www.halti.co.uk/halti.php
Joy