This has obviously been a fun thought-exercise for many of you, but I think what's at heart here, the "skill" we're eager to develop via exercise, is just plain old good communication. In the entrepreneur example, the failure is not his inability to BE more specific, when asked. The failure is that he doesn't already KNOW he hasn't been specific enough. So, the skill we need is not how to muster specificity when Paul Graham asks for it. What we want is simply to be able to communicate abstract ideas clearly in the first place.
All these conscious exercises of ever-increasing specificity miss the point entirely.
I don't have a developed exercise idea, but I was inspired by the following, which I happened to have been reading earlier today.
That is the original proposal for the World Wide Web, written by Tim Berners Lee at CERN. To read that document in 2012 is, itself, an exercise both useful and relevant to these discussions. The document is chock full of descriptions of things that did not exist in 1989, but which have now become mundane and ubiquitous. Tim is in the role of the entrepreneur trying to explain what he wants to build and why. One can't help but be astounded by the ease with which Berners Lee renders clear enough description that we can recognize all the specific things that have arisen from his "sketch".
For example: "Meanwhile, several programs have been made exploring these ideas, both commercially and academically. Most of them use "hot spots" in documents, like icons, or highlighted phrases, as sensitive areas. touching a hot spot with a mouse brings up the relevant information, or expands the text on the screen to include it. Imagine, then, the references in this document, all being associated with the network address of the thing to which they referred, so that while reading this document you could skip to them with a click of the mouse."
This is exactly the kind of context where we want to help people to be as specific as possible, when they are trying to invent something.
Exercises in categorization or "lattice-travel" seem to miss the point entirely. What we want is simply for people to choose the best language for their audience. The only remedial program I can recommend for for that is trial and error.