When Dexter started his barking at everything phase, instead of trying to figure out why he was barking I tryed to shake a can of penny's to quiet him, he barked louder and lunged for the can of penny's, took it, rolled it on the ground and played with it and "killed it" I am pretty sure If i ever threw it he prob would have chased it.... needless to say that method def didn't work for us, and I realized that the same thing dose not work on every dog, there are no quick fixs when it comes to any animals behavior (human or canine)
Dogs are creatures with feelings emotions If you believe your dog is barking out of fear, i wouldn't recommend punishment to try and stop it! You have a very young puppy on your hands kinda like a pre-teen, very impressionable, still learning, still bonding with you learning to trust you. Throwing something at the dog to try to stop a behavior may stop the dog from barking, but why was your dog barking to begin with, because he is afraid? Now that doesnt seem very fair, teaching your dog to listen to you out of fear will more then likely damage your relationship, and your dog will learn to not trust you.
A better way, when your dog starts to bark (if you learn to catch your dog right before he starts even better!) redirect him to you, Once you can get his attention away from whatever is scary and he stops, give him something he REALLY loves, maybe a delicious treat, a tug game, a job, sit/down/stay for a treat? I personally don't want a dog that respects me out of fear, I want a relationship that is built on mutual trust.
If your dog is sacred of something he needs to know his "leader" is there to protect him to call the shots about whatever it is that is scary. Its really not fair to punish a dog for something he doesn't understand is wrong.
The what were the instructions the trainers you used before? If you are not happy with your current trainer, there are bundles of great trainers all with many different methods and ideas you could always look into as well... i am sure you could find great recommendations on this board. In the meantime I also second, Teaching your dog how to speak and be quiet on cue for fun and bonding