With the growing Blightun air threat the allies needed a dedicated anti-air weapons platform. With its four machine guns and armored chasis the Polsten Quad Gun fits the bill and then some.
The Quad Gun is the superior anti-aircraft unit. It's Air Range of 2 is best used with this unit up away from the deployment zone so it has as much coverage as possible. No need to deploy this unit first sign of aircraft. Allow the Blight to move up the board or even into your territory so you can get the drop on them with deploying one of these.
It's 2, 2 die attack against planes and infantry means this unit can put some serious heat on Aircraft and Panzerfaust. Keep it close to your armored targets to ward away direct attacks from these units.
Consider putting an anti-armor plug to offset its inability to defend against tanks. However another plug with an air range would also solidify it as a terror for Blight Aircraft.