Sorry. Just saw you asked about the wet paper towel. You want the center to be about room temp when you pull it off the grill. So you let it sit out to warm just a bit. You do not want it totally exposed. Two reasons: 1 keeps any flies or any crawling bugs off it (as you know fish attracts them. Like crazy), 2 and this is more important, it maintains the moisture level even between the center of the meat and the outside. This way you do not have to put oil or anything if you do not want, and the seasoning will still stick.
Your cook looked great! I was supposed to be out fishing for them today, but Mother Nature did not want me to and turned on the fan. Too much wind. I love yellowfin! And bluefin, and longfin, and black fin, and bigeye.....