When i had both bryopsis and hair algae, I used hydrogen peroxide. 1/4 peroxide 3/4 tank water and let it sit in there for about 20 seconds. Everything fizzled away and I ripped off the long pieces before putting it back into the tank.
Another approach for large pieces of rock which hydrogen peroxide is not practical, I grabbed a five gallon bucket during a water change and filled it with tank water. I grabbed the rock and scrubbed it with a tooth brush removing any sort of algae i could find/remove. If you have corals on the rock, just be careful and avoid hitting them with the bristles of the brush, use an OR grade hemostat to remove hair algae under any corals if you are "lucky" enough to have HA growing in between them. After you are done scrubbing and removing, keep an eye on the frag or rock for any attempts of the algae to grow back.