I agree with your post, trying to succinctly explain an idea is invaluable in a lot f ways. My problem is, I find myself keeping the word count down by keeping things vague and I'm still trying to become more specific (usually with my character's intentions) within the word count. I imagine the day I figure this out is close to the day I sell my first script, but I will always be a student.
I don't agree, however, with your comment Foxtrot, that screenwriting is two forms of writing. You have dialogue and action, yes, but I don' see them as separate from one another. They should work together to elevate each other and the piece as a whole. Simply, action tells the story and dialogue gets across character (although both should tell each other, in between the lines). But, if you wanted to break it down, I would be hesitant not to include the fact that even well done scene headings, transitions or a parenthetical can dramatically shift the whole mood of a scene. Thanks.