“Let’s flesh out the details of the plan”
“Let’s flush out the details of this plan”
These phrases are so often interchanged, and it bugs me! So let’s figure this out.
Generally, you “flesh out” details, not “flush” them out. Fleshing out is a phrase which comes from the art world, where you start with a skeletal body, and then “flesh out” the rest of the image – adding “flesh” to a skeleton. Get it?
Flushing out means to bring out into the open; police may “flush out” a criminal from his hiding place behind the toilet. I’m not sure what it would mean to “flush out the details of the plan” – somehow the details are in hiding, waiting to be revealed, and you’re going to scare them into the public?
Sorry for being a word snob.