On me old Mini we ran a length of pipe ( the kind you get from a per shop for your fish tank ) from the washer bottle , around the engine and then to the washers in the bonnet - when the car warmed up , it warmed the water up and sprayed warm water onto the window. It dint help the initial freezing , but after 5 - 10 mins it got rid of the problem.
This is a modification that I've seen on many classic cars, but specifically, the pipes are routed around the coolant pipes where they get hotter first. It works even better if you replace a short section of the coolant pipe and washer pipe with copper pipes (big and small obviously) and wrap the small one around the big one in a spiral.