Only tried this on one of my lorry kits, but...............
Following painting, and allowing time for the paint
to dry thoroughly, wrap clear tape around the
exterior of the window openings.
Fill the window cavity with Micro Krystal Klear, or
Glue n Glaze. Use a cocktail stick to pop any air
Leave overnight, to allow the glue to set. It will
change from milky white to clear when ready.
Remove the clear tape carefully.
You now have a glazed cab.