My Collie is 2 years old and yesterday he was scared of the stuff dog toy at the local rescues fund raiser

Hackles up tail up barking and growling

How I deal with that is slowly walk him up to the object with me in front I touch it he then smells it and works out its not going to eat him or me alive!
That has worked so far for me with him for bin bags, balloons and all other strange and dangerous objects.
I never use punishment methods ie water sprays loud noises ect as I took him to a puppy socialization group and the trainer sprayed him with water, Toby completely panicked and the guy told me I was being to soft with him! Even though he'd scared my ten week old pup half to death. I didn't go back.
Sometimes it doesn't matter how much socialiation you do with a Collie they will be scared.
I would try with your dogs exercising them with one or more high energy confident dogs ( like golden retrievers) to distract him from any loud noises hopefully! Or use his favourite toy or food when he's scared to coax him out of that mind set. Try and distract him any way you can and see if it helps.
The other thing you could try is desensatising him to noises in the home ie start with not to loud a sound, maybe a wooden spoon on a pot and have someone feed him at the same moment eventually the dog should begin to associate loud noises with a treat. As you increase the volume. Maybe you could play a recording of fireworks going off.
I'm no expert but these are things that I would try with my dog if I had a similar problem. I hope you find a solution.