the aim is to wash away the grime OFF the windscreen not just move it around and smear it.
place towels on dashboard as it will get wet otherwise
use a fresh, cleaning mitt
bucket with car shampoo, dish washing detergent or similar with warm or hot water
soak the mitt in the soapy water and wash the windscreen
clean the soapy water off using a window squeegee - go from top to bottom but do not lift it off the window until the end
then use a dry glass cleaning cloth to clean up any residual soapy water