I have a UV light on my tank which grows incredible amounts of hair algae on my Anubias. Every year I pull it all out, soak it for 3 minutes it a 10% bleach solution (that's 9 parts water to 1 part bleach) for 3 minutes, then toss it into a 5 gallon bucket of fresh water.
Once I've dipped all the plants for their 3 minutes each I head over to the 5 gallon bucket (that is now full of anubias and fresh water) and use my fingers/thumbs to scrub it off. BY now it's all turned white and is dead so comes off easy.
THen I rinse it all under tap water for a few minutes (continue scrubbing off the dead algae if needed).
THen it's back into another bucket of fresh water (treated with a double dose of declorinator) for half an hour and then it's back into the tank.
THe whole process takes quite a while since I have to re-secure the anubias to the drift wood, but it's worth it.