Create a new layer and place it above all the previous layers. Paint it in black color with Paint Bucket Tool and apply the filter that is shown here: Filter - Noise - Add Noise.



Selecting the Motion Blur, it's possible to blur out this layer:



Change the layer's type on Screen and make the appropriate corrections on its brightness and on its contrast (ctrl+L).



Blur it out also with Filter - Blur - Gaussian Blur.



Select the Layer Mask and Gradient Tool to hide the lowest part of the layer.