I did this one time when I saw a particularly beautiful scenery. I could remember the elements mostly, but didn't quite manage to capture the beauty of it.
I try to paint them as soon as possible after waking up.
Usually I just write down a list of keywords, that seems enough to keep my brain from erasing them. I don't think it's really possible to capture a scene in text. The text only serves as memory aid.
Yep. I've started painting my dreams and it is surprisingly difficult to turn vague memories into concrete scenes. It's almost physically exhausting.