Can you use orajel on a dog?

No, Orajel is not designed to be safe in the ear canal. Also, there really isn't any reason to be pulling ear hairs on a dog - they are there for a reason (to keep your dog's ears clean) and pulling them out can predispose your dog to ear infections. It's also painful to the dog, as I'm sure you have noticed based on your question.

If your dog is having chronic ear infections, I would start with keeping your dogs' ears clean and dry, and possibly clipping the ear hairs close with a small pair of scissors.