If you use the dryer, you might want to wipe it out before drying anything more in it. Sort of a case of not wanting to use the stuff on things that don't need it.
Here are the Department of Defense instructions for using Permethrin and Deet the most effectively.

Note that permethrin is deadly to cats, so keep cats well away from permethrin treated stuff as well as the spray.
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May your trails be crooked, winding, lonesome, dangerous, leading to the most amazing view--E. Abbey