Equalize reflection of photo of polaroid photo?

[denzjos]

What I did (a fast edit):
Copy the photo to 2 new layers (let say layer 1 and 2)
Use layer 1 'Colours / Treshold' use the slider so you only see the reflection
Select the reflection (black) from the treshold layer 1 (use the 'Fuzzy Select Tool)
Select layer 2 and delete the reflection with the selection
Set layer 1 not visible
On layer 2 set layer mode 'Multiply' and use 'Opacity' to correct the color and lightness 
Use 'Colours / Hue-Saturation' to correct the color and lightness
Make a new layer from visible (layer 3)
Correct the edge of the reflection with the 'Healing Tool' on layer 3
Use the 3 picker pipettes from the 'Colours / Levels' to adjust the colours