There are horse earplugs on the market that might make it less scary. I've never used them, but I've heard they work.
You can use scissors too, if using clippers move slowly and don't turn it on at first, just rub them along his neck moving up making noise with your mouth and then try with clippers on
Put a towel over his eyes or twitch him
Put a cloth in their ears it may help with the noise.