Rain storm approaching Brora

I used to do a lot of burning in skies on photographic prints when I was a student. Photo editing is meant to make this all-so-much easier now. Except I'm still pretty ham-fisted at Photoshop and have never found it terribly intuitive. So this is my attempt to reproduce what I saw at Brora today. It would have been a lot easier if I had remembered to bring my graduated ND filter.