NOTE: the following is my n=1 experience and I have no scientific basis for this information.
Anecdotally, I have noticed somewhat less soreness and general overall good feeling since I started taking regular Epsom salt baths. I generally dump about a cup (eyeballed, no actual measurement) of salt into the tub, start filling with warm water, slosh it around a little to dissolve the salt, sit with my legs submerged as the tub fills, then eventually slide "down" so my upper back and shoulders are submerged for a few minutes.
I agree that there's no need to overthink the specifics. Dump in a generous amount of salt, full the tub with nice hot water, enjoy.