Very neat job Wayne, and one I'm certainly not looking forward to!
Guttorm, if you could post or e-mail a pic of the window, it would be very helpful, thanks.
CR, I can't do it these days, as my hands let me down, but that's the way I used to do some framing once, using pre-painted and cut strips of ordinary 'Sellotape' (clear parcel tape/ Scotch tape etc). Lay out on glass (preferably), paint, cut, stick, seal with clear gloss, then clear coat matt (if required) on the strips with a 000 brush.