Hi When doing and overlay which should have translucent glass I cut out all the glass and I add new layer under it filling it with white gray or light blue atc ( dependind on what color I want the glass to be)
And than I play with the transparency of this layer till it has the translucency I want.
In your case si there are ornaments so it will need more work with the cutting out but this is what look in my opinion most natural.
Or you can just simply put the cut out whole windows to new layer and reduce the opacity… but then it will make translucent also the ornaments and the “glass” will have still the background visible there “above the character” so it will be bit less realistic