Magnetic CH cleaners

Referring to the generic magnetic filters rather than any one manufacturer.... Some models have a drain valve allowing you to empty the container which then you can refill with any CH chemical. Other models don't have this drain valve but you can syphon the water from the filter container. The latter models tend to be shorter in length for fitting in smaller spaces. The CH chemicals will then get circulated around the system when you re-assemble the filter, release the isolating valves and run the CH system as normal.

I understand that is the principle, but surprised it's little advertised for the DIYer.

You can also get inhibitor concentrate that makes dosing that much easier.