Some things that helped me with my mouthy Shiba Inu puppy:
1. Hand-feed him
You can try and teach him some bite inhibition. Hand-feed him some kibble one by one. If he bites too hard while trying to get at his food, yelp in a high pitch, and ignore him for a few seconds. Then start feeding him again. This way he learns that biting hard can hurt humans and when he does that, the food and attention stops. Hand-feeding is also good for bonding and establishing your leadership.
2. When your dog has his mouth on you, it is important NOT to jerk away. Jerking away will cause you to get scratched. More importantly, sudden and quick movements may make your dog think it is a fun game and reinforce his biting/mouthing behavior. At worst, quick movements may instigate your dog's prey drive and cause her to get aggressive. Instead, stay still and either give a No command or yelp as a puppy might do to his litter-mates when they are playing too rough. I use the yelp for puppies who are still learning and for accidental biting.
3. Yelping will startle your dog and cause him to release his mouth. Quickly follow that up by redirecting him onto a toy. You don't need to shove it in, just put it there for him to bite on. When he starts biting and playing with the toy, praise him and play with him.
4. If your dog persists and keeps biting on you even, then stop interacting with him and ignore him.
5. If your dog amps up his biting and tries to bite your leg or clothes when you are ignoring him, then say "time-out" and remove him to a time-out area (a safe but boring room, e.g. laundry room). Leave him in there for a couple of minutes and let him out. If he starts up again, non-mark him (ack, ack), and say time-out and put him back in time-out. This time lengthen the duration to about 10-15 minutes. Note that if your dog stops the biting behavior, make sure to praise him a lot and give him good treats. Keep this up and your dog will learn that certain behaviors get him rewards while others get him into a boring room with nothing to do.