first of all tweak the levels, push the right bar(white across to the left until it pulls the brightness back up to something realistic.
then using the contrast by about ten points to remove the mist
then using the burn tool at 5% from the dodge and burn, apply this to the fore ground objects to hide the trees that have a distinct outline
apply this to the mountains so they are a little darker as well.
reverse areas with the dodge tool 5% to pull some places back up.
This gives the effect that clouds are crossing the foreground plain out of sight from the cameras view.
apply one sharpen filter
burn the mountain range so it blends more with the base of the mountains and the ground.
use the color balance tool and push the green +15 and the yellow - 15 to ramp up the colours a little more.
you can tweak the pixels in the sky at the top of the mountains for a better result
also compare the result on LCD, they dont hide anything like a CRT does.
edit: yes the clone tool would help as well but zoom in and use sparingly with a small brush.
then burn and dodge over it.
use the [ ] keys to size the brush quickly.
those results will appear like this.
