If you hunt you know you have to hunt the wind. Wolves do it, all natural predators hunt the wind. You also know that to an animal, a human stinks. One whiff and they take off to the next county. Some folks use bic lighters, flame blows in the direction the wind is blowing, problem is it's only good for the wind right where you are and it doesn't help you see what the thermals are doing. Others pack small bottles of talc and a little squirt and you can watch the powder drift, though it isn't very visible past a few feet, and it smells. Lots of folks recommend Milkweed seeds but I find them to be a bit messy to carry about.
For me Cattails work so much better. I just cut a bit off the top, not much. Pick it a bit and the pieces will begin to float out. It's easy to do, also they tend to hold their shape real well. I carry mine in my pocket, pull it out when I want to check the wind/thermals. You can watch them float for a long long way. I once watched them float on thermals as the sun was setting for 10 maybe 15 minutes.
In the first picture below you can see them slightly to the left floating down that old logging road, some of those are a good 40 yards away and still visible, they also ride thermals so you can tell where your scent is flowing even if there is no breeze.
Keep the wind in your face.