If the width of the window is 1.5 feet (18 inches) what is the length of the squeegee you are using?
If your squeegee is shorter than the width of the window, i would be fanning it. If you are having a little trouble with this, why not try practising on your own windows until you feel you have the knack? Takes a little while but you will get there.
If the squeegee is longer than the width of the window, I would hold the blade vertical against the left hand edge of the window frame, with the top edge (of the blade) in the top left hand corner of the window. Then move the upper end of the squeegee along the top edge of the window until you reach the opposite (top) corner. Next guide the squeegee down the window (it will of course be at an angle) until the lower end of the squeegee meets the lower left hand corner of the window. You then need to guide the squeegee along the lower egde of the window until it reaches the lower right hand corner. The squeegee should then have covered the whole of the window.
Hope this makes sense and is helpful.
John.