flesh-out vs. flush-out

First of all, let me say that both of these sayings creep me out.  The act of "flushing out" or "fleshing out" and idea or object seems weird and gruesome.  But, I was strapped for a phrase in writing my semester paper for Spiritual and Ministry Formation and had to use fleshed out.  Shudder.

The kind people at Washington State University (via Google) explained the difference between the two phrases (there is one):

To “flesh out” an idea is to give it substance, as a sculptor adds clay flesh to a skeletal armature. To “flush out” a criminal is to drive him or her out into the open. The latter term is derived from bird-hunting, in which one flushes out a covey of quail. If you are trying to develop something further, use “flesh”; but if you are trying to reveal something hitherto concealed, use “flush.”