the first one, you could likely do by creating two additional layers.. one you paint completely with a charcoal shade, the other set to a dark blue... you'd set the blue layer to an opacity that suits you... usually, quite transparent,  the charcoal , you'd "Send to back".. the clouds, you'd carefully use the eraser in brush mode, set to fully soft, and opacity set so that you create a faint transparency that lets the lower layers show thru, darkening the clouds. It takes some experimentation, but the results can be very striking. If you're working with a black and white picture, you can leave out the blue layer. The second one could be created a number of ways... most of which depend on what you have to start with when you go into post. Lou.

"..... and that was when things got interestiing."