I can see it in my mind's eye...
Budget constraints will, of course, require the use of battered old Stearmans piloted by grizzled ex-cropdusters who've lost their licenses due to various improprieties.
The chemicals, however, will be top drawer stuff... 24A, the best darn Arabicide that money can buy.
Training will be brief. You open the valve when you hear stones begin to strike the underside of the aircraft. You close it after the stone impacts have tapered off, and then stopped.
As always, loaders and flaggers aren't paid until the trucks are gassed up and parked back at the hanger. You know how they are after they've got that money in their pockets.