I bought some Permethrin today.

How do you use it exactly? Do you just spray it on all clothes? Is it safe on synthetics? Does it give your clothes a foul odor?

I guess my main concern is sweat. I sometimes hike in cotton long sleeved T-shirts and on warm days I can sweat quite a bit into the cotton shirt. Does the Permethrin leach out with a foul odor? Does it get greasy?