There is a video done by BRS about it and I followed their recipe and it worked great rocks came out super clean and after process completely bleach free. I then cycled the rock for 2 months with zero issues with leaching PO4 or anything else.
Bleach works great but I get your worry but it’s actually very simple and easy to do. Other method would be acid bath them. This in my opinion is the crazy option.
I had a bad battle for with Dino’s in my system. I dosed up to .08 -.10 and just kept them steady there and they disappeared in about a month. I now just maintain the .08 and I have never seen them again
So in my experience you can either up the dose but not to exceed the natural daily evaporation of your system. Or you can dose a more concentrated slurry to your tank.
I am running a Kalk reactor by avast and I dose about a cup every two weeks to it.