Can't say as I've heard of a 'swat' switch before. Squat switch perhaps? If so, it's a 'weight on' switch that protects the landing gear from being raised whilst the aircraft is on the ground.
I've not worked on a Duchess for a long time but you'll find two types of feathering accumulators on light aircraft.
One is a long tube about 15 inches long and maybe 3 inches in diameter that is generally mounted towards the rear of the engine on a metal plate. The nitrogen charge is around 90psi depending on temperature.
The other type is more obvious as it's part of the propeller hub. If the spinner is two-piece (the forward part held on with three screws), there'll be a charging valve underneath. According to temperature, the pressure will be around 20 psi.