Well i have battled cyano many times and found the best way to get rid of it on the gravel is to go in by hand and remove the top layer of gravel/sand with the cyano. put it in a plastic bag and wash and drain in the bag the cyano will float to the top, then let it dry before putting it back in the tank.
If any on the glass or rock use a toothbrush to remove as much pulling it off in strips/sheets. Then scrub the area of rock or glass where the cyano was with the toothbrush. This is a royal pain to battle.
It will keep coming back until you get the water right and i determined my problem would occur after I siphoned the gravel during water changes and stirred up the substrate I will only do that to a small portion of my tank bed at a time now.
Get your water right, do not use tap water, do a good water change, dont stir up the substrate.
like I said this is a pain, and you may have to repeat in a week, but since I figured out it was happening from stirring up the substrate I havent had a problem with it for over a year now.