If successful, please explain how you trained your basenji to walk off leash. My girl is approaching 8 months and I would like to teach her while she is still young.

I know it is hard and maybe not possible for some basenjis but I am willing to put the time and effort in.

My girl is 7.5 months now and she is great at not pulling on walks but I would like to use a martingale collar. While she is not fully grown would it be beneficial to buy a 12 inch collar (i think this is the correct size) or what for when she is fully grown?