For most briefs I sit next to the stude with a model and a few sheets of A4 paper and build-up the story. For Nav I find the white board useful (because it's bigger!) and for relatively complex things that need good pictures (like asymmetric theory) I use prepared pictures on acetate - these can either be projected on an OHP or used on top of a piece of paper.
(BTW, I've been in the IT techie business for 30 years but avoid presentation software unless it's a large audience, and even then I'm dubious of the value of it).
HFD