Velcro, heel straps, I do not go anywhere out of the shower or bed w/o proper footwear! And, I've gone as far as 40 feet before 'noticing'.
You are going to have to get him soo very aware that this is to be treated as IF one has a diabetic neuropathy....It's not gonna go away, and walking around in socks or shoeless means one can step on 'things', bad things and not know it. Period, no ands ifs or buts.
It is a retraining, but one of self-preservation...diabetics get cuts on their feet that can go un-noticed and turn into those nightmare nasties...
Melody - I know you will work on this. It is essential. Take care - j

Joe, it's when the eyes go weird or bad tho, that things really get interesting! Sort of....