AG Woodcare suggest 2 - 4 tablespoons in 1 pint of hot water (For wood bleaching)

You might as well make it more concentrated rather than less, even saturated many suggest.

You can thicken it with wallpaper paste so that it clings rather than simply running off onto the ground.

Ammonia or borax is the recommended solution for neutralising it an wood and stopping the bleaching action but on grp or spills just use washing soda or bicarb or just wash away with water. Bicarb or just water on you.

Take care but it is not as nasty as many things I could name. I remember the days when we pipetted a near saturated solution routinley by mouth!