I don't consider sex scenes a slog a slog, but I totally get you on how difficult they can be in relation to other things. Anything with complex choreography is always hard, and it's like, a normal writing day I can pull off 1500 to 2000 words, but you put in a sex scene, 500 words is an excellent result...

Also I'm finding that while some images might "magically arrive" the way you describe about other imagery, it is still a lot more exhausting to try to translate that into something that has a shot of giving a reader the same image.

Congrats on finishing your sex scenes and good luck with the action scene!