Training samoyed on halti

Start by getting him used to it inside the house, just leave it laying around somewhere he can see it, so it isn't a completely alien object to him. After a couple of days progress onto putting it on him (no lead attached) and feeding him REALLY high value treats and something he gets at no other time other than for halti training (something like cooked liver, small cubes of cheese or hot dog sausage). Continue doing that several times a day for a couple of minutes, for about 4 or 5 days.
 
Then you can move onto attaching a lead to the halti, and try to slowly walk a few steps, using the high value treats to coax and reward him for every step. When he is happy with this, you can progress further by trying to walk him for further distances out in the garden, all the time using the high value treats.
 
Its a slow process, but it'll make him associate the halti with good things (treats) and then eventually going for walks. They're very strange things for dogs who have never worn them, and they can't be expected to just have it put on and begin to walk properly straight away, it takes time. Invest in something called a halti link, which is a little strap that attaches the halti to your dogs regular collar, so IF the dog does manage to slip the halti, your lead is still attached to his collar, alternatively, you may want to try a dogmatic headcollar, which in my experience are much comfier for the dog, since they don't ride up into the eyes, and I've found dogs seem to tolerate these better.
 
Good luck! In the mean time, whilst he is getting no exercise, make sure you do lots of mental stimulation and games with him, won't you!