hot water pressure loss/new valve flushing

I am having a loss of pressure on the hot side of a couple of fixtures after installing a new shower valve. I would guess that there is some blockage. How do I solve this and why is it not in all the hot side fixtures. I removed the "screen" on the faucets and that solved teh cold side blockage but now hot is blocked on sink and shower side on hot side only Also, when and how do you flush a new valve? Thanks, Pete

You may have to turn off the water, dismantle the faucet, lay a towel over it, and then turn on the water pressure very briefly to flush out the debris that is clogging the hot side.
Good Luck!
Mike