Thanks for the tips everyone.
I am going to try ospho to scrub out the rust, since it is surface mostly. Then try to find some kind of "encapsulator" that I can soak down inside areas I can't get to, that is a good top coating. Apparently ospho is ok for scrubbing it out/ lasts a year or so, but needs to be top coated.
Just to save the time, yes I do know about the adhesion issues related to epoxy( specifically SPI) and Ospho.
Also thinking of something like a flexible small bottle/bore brush chucked up in a drill that I can snake inside stuff just for good measure.
Will check out the Rust Fighter by 3m as a top coat option for the areas I can't get to.