Well, I am one of those on here whose littlies LOVE their clothes...which seems odd when you consider that I got Brody when he was 14 months old and he never wore clothes until I'd had him 7 more months, and that Mia's former mommy would dress her up but said she didn't like it. Mia is only 6 days older than Brody, but both Brody and Mia were 17 months old when Mia came to live with us.
I see other good suggestions have already been made, but you might try putting garments on J ONLY when he is getting a special treat...cookie or trip somewhere that he loves to go. If you can associate the clothes with that special thing and get him used to getting it, you can expand his wear time...I'd make it two-fold...a trip somewhere and a special treat he only gets...at first...when he wears the garments.
BTW, the first garments I put on Brody and Mia were jackets for the cold. These were not full coats...just like a 'shaped quilted placemat' with velcro'd straps under the tummy and around the neck. They LOVED them so much the showed obvious disappointment on their faces when I took the garments away, and were jumping up and down, grabbing at them, trying to pull them out of my hands. Maybe if you try something like that at first...they work to keep body heat in like a hat does...on the top.
Here's a photo...