Many trappers mark trap locations or “nearby” locations with marking tape.
Conibear traps are used above the waterline. Coninbear and conibear cubby traps pose a greater danger to dogs in Minnesota than people realize. MN DNR limits the size of the trap above the waterline, but that size is still large enough to get a dog. I would say snares (for coyotes) and leg hold traps (fox) are more common in ag land.
The trapping organizations are trying to educate their members to be more cautious in their use but it just takes a few guys out there running aggressive old school. Most dogs killed in MN appear to be dogs of rural people running off leash but bird dogs are not immune from the danger.
Wisconsin rules are a bit more stringent and greatly reduce dog’s being hit.
Large plastic zip ties work really well in opening the jaws but can become brittle at cold temperatures.