[policarpo]

For what it is worth, I'd use a mindmapping app like Novamind for all brainstorming and preplanning. It's a lot more fluid to maintain during the initial stages of any project. It will also export to OPML which plugs in nicely to OmniFocus.

My typical workflow is this:

. State Purpose as Central Node in Novamind
. Branch for Goals
. Seed Nodes for brainstorming (I use Lateral Thinking for brainstorming)
. Processing & Declaration of Concepts
. Next Steps Defined in a new MindMap Tab
. Export Next Steps to OPML
. Import to OmniFocus
. Process
. Review
. Do.

My projects are never of a scale where I need to use OmniPlan...plus I work with PM's who use OP so I don't really need to spend time in it.