Canopy Weathering

Not so fast - the canopy may be the only thing that's clean, but unless the aircraft has been sitting or is just back from a mission (maybe bugs and/or engine oil on the windscreen), the canopy is going to be as clear as the crew chief can get it. Seeing is living. I agree that the frame should be weathered. Of course, if it's been left out for a long time in all weathers, an aircraft's plexiglass might be a little yellowed or crazed in places. That (and the bugs) would be special in 1/72 scale.

Try brushing dull clear coat on the clear parts just inside the frames. Leave the center of the panel clear, as if it was hastily polished with a rag, and they didn't bother to get into all the corners of the frames. Sometimes, I'll lightly dust the whole canopy with the flat coat, especially if the airplane is weathered with a lot of dust.

I'd weather the canopy the same way the rest of the model is weathered. Give the frame a light wash to dirty it up a bit. Maybe some scuffs where the guys grab onto it and that'd be about it. You could maybe put some light scuffing just below the canopy sill to simulate boot marks. Hope this helps!