Crazy expensive stuff but I admit to using it. Run it through the flush port after every use. Try to do it while the engine is still warm and the t-stats are still opened up.
I've used white vinegar inside a power head to clean out the salt and scale. Some also squirt Dawn detergent down inside their hose, before turning it on, then flush w/ that.
Vinegar is a polar solvent to salt, which is a polar solute, therefore vinegar readily dissolves salt.
Just an FYI. I too have been using Salt Away for a few years now maybe every month or so. I always wondered about the maximum benefit considering the T-stats probably closed pretty quickly once the cold water (with Salt Away) hit them. With the post hurricane blow today, I figured I would use the day for some prevent maintenance. One of the things I did was a Salt Away flush but this time I did something different out of curiosity. I hooked up the Salt Away attachment and turned the hose on while the OB was tilted down. Then I started the engine. Within a minute or so I started to get that Salt Away "soapy" residue behind the OB. I let it run until the resevoir was almost clear (of Salt Away) then I shut her down and tilted up and finished the flush until the bowl was clear. It was pretty clear the Salt Away was getting plumbed through the OB with the soapy residue behind the boat and obviously the t-stats were open. How much of a benefit, who knows. But I thought it was interesting and I will probably continue doing it this way for awhile.