I spray my boots, socks, pants, shirt (and tee shirt) and cap. Make sure all is dry. I actually have two sets of treated clothes....and I use a Marker to identify the tee shirts and socks so that I know the treated from the non treated garments. My wife appreciates it when sorting laundry.
I also spray my tractor platform and seat area.......and spray our golf cart and 4 wheeler floor boards and underside.....to reduce ticks hanging out in those areas. It doesn't take much. I have considered spraying around my shed to keep ticks out of work areas.
THIS same spray on the carpet in your boat will keep biting flies and horseflies at bay. Great use!