What about soaking it in a brine or a marinade? A long marinade can make it mushy, so under an hour if you've got an acid or base in the sauce, but a brine can soak for as long as you want.
learned a little trick from a deckhand , he said marinate it or not but before you put in on the grill smear it all over with mayo, i do it , it also helps it from sticking to the grill, i do a light teriyaki for about a hour than lay on a little mayo and hit the grill, i also like just olive oil , garlic and other italian type spices then repeat with a littel mayo
Im gonna have to go with mason jar also.Broke out 2 jars just the other night,ate the tuna straight outta the jar.I actually beleive it was tastier and more moist than ever.Soo damn good.
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I fish for sustenance,I suffer from sustenance abuse.
Marinade in creamy Italian dressing for a half hour then wrap it in aluminum foil and throw it on the barbeque or in the oven. Stays very moist. Same process works with most any fish.