You mix it with water & use a sprayer to apply, just as you would do with Poultry Shield. However, you should wear protective clothing & mask as it's nasty stuff which is why it says for professional use only.
My husband wears one of those disposable overalls, gloves & if there's no hood, an old shower cap - he looks a treat!
He also has a filtered mask he uses for his work too.
Wash the sprayer out well after you've used it, making sure it doesn't go into any streams or rivers. Have a shower afterwards too, to be on the safe side.
It really is the business but it must be used carefully.