Best way to deaal with a NATO jumper is to pour avgas all over it then throw a match on it.
Then go down to PIRMARK and buy a fleece of your choice. When said fleece becomes a safety hazard due bacon grease, BO etc. Just bin it and buy another one.
The body warmer type fleeces I found the best as they allow your arms to be free without your sleeves catching on anything. And if you get cold on a navex you can pull your arms inside to keep warm.