Well, I spent most of the day washing clothes and running errands, and then working on the riding mower; it's about to start its 15th cutting season. Main issue right now is a dead battery, which I have put on a charger to see if it can be revived.
I looked at the winch wiring and found that the forward and reverse wires from the winch are wired correctly to the butterfly direction switch. However, the current on-off switch appears to only interrupt the negative lead to the butterfly direction switch; the positive lead goes to the battery box. I still don't have a battery yet, but I used my battery charger to check operation of circuits. The Camdec solenoid is wired to the ATV ignition switch and operates as previously described. I hooked the charger to the winch positive lead, but I couldn't get the winch to operate; the charger probably doesn't put out enough amperage. I know the winch was working properly just before I bought it.
I used a multimeter and checked the Camdec solenoid off the ATV. There is no continuity between the opposed lugs when there is no power. I clamped the negative battery charger lead to the mounting bracket and touched the positive battery charger lead to the small lug; it clicked as before. I left it clamped to the small lug and checked the large lugs; now there was continuity between them, so the Camdec solenoid appears to be working properly.
I will put the winch on-off switch in series between the Camdec solenoid small lug and ATV ignition switch and re-wire the positive and negative leads to the butterfly direction switch, and wire the Camdec solenoid main lugs in series with the positive lead. This arrangement looks similar to the wiring diagram in the manual.