I must admit I haven't because it's gotten to the point that if I even approach him he swallows it. I can try throwing a treat at him. He's pretty keen on leftover chicken this week!
You could also try classically conditioning a reward word; a lot of people do this inadvertently with words like "treat!" where the dog learns that "treat!" means something yummy is coming so they will book it over and look for their treat.
Just sit down with something relatively high value (boiled/baked chicken works really well for us, since it's valuable but also not super rich) and say your word, give a treat, say your word, give a treat...over and over again. That way you don't even have to approach, you just give the word and pup comes running, looking for goodies. It does take a lot of practice, though.
I do agree with another poster that suggested muzzle training as a possibility; IMO it's not a bad thing for any dog to be muzzle trained. I know the Muzzle Shop has a lot of options and some are really cute; plus, they're lightweight and inexpensive.