When J is on the verge, or in the midst, of a tantrum, there are two steps to calm him down. Both are required.
1. Remove his shoes. If he's not wearing shoes, well, he isn't really throwing a tantrum. I don't think.
2. Hug him so he's laying on your chest, rub his back, and sing Mama's Gonna Buy You a Mockingbird.
Nice to know that the same song that soothed him as an infant still works (and possibly quicker) on him as a toddler!