I have extensive experience glassing boat hulls (from kayaks to 40 foot hulls. I suggest smoothing the centerline front to back first. Use push pins to hold cloth in position in the centerline. Then smooth the cloth down to the edges about midway back on the roof (fore and aft centerline). Then smooth in each of the four quadrants at gradually increasing angles towards the front and back using the palm of your hand gradually working the wrinkles aheadnof your hand towards the corners. This does the same thing as tuggingnon the corners but if done gently and patiently and gradually – is easier on the cloth. The push pins are your second,third,fourth set of hands.