I use Cypermethrin and Deltamethrin (think I spelled them right) for spiders and scorpions.

I see a lot of black widows in the brushy areas on my property (cactus and mesquite), but very few in the areas I've cleared for outbuildings. Cut down brush around inhabited areas. That's the most effective thing you can do. Get rid of rubbish (fallen wood and such) near dwellings. Wear gloves when handing wood.

My stock tank is usually dry, otherwise I'd try to get a colony of mud daubers started. The dauber's preferred diet is spiders (crack open a dirt nest and look at all the spider carcasses inside). I think it's the organ pipe dauber that has a preferred diet of black widows. If you have a steady water source the wasps can draw from, you might want to try to establish some daubers in the shed. Daubers aren't aggressive. Don't know anyone who's ever been stung by one. They can sound aggressive (buzzing their wings furiously on top of their nest), but that's just their way of circulating air to dry the mud after they daub it.

Check your boots in the morning and your bedclothes at night and you should be all right.