I have heard of guys using an umbrella to hide their infrared signal from FLIR.
I watched an Apache FLIR video from A-Stan where a Tolly-Bon walked into the hot smoke and hot ground of a grassfire- and utterly disappeared. His buds that ran up a hillside, got smoked, one after another with the 30. The Apache gunner gave up on the Invisible Man, and went after the runners.