He explains here.
I thing it can work well both ways, but I agree that there are some great benefits to going notes-free, or more-or-less notes-free.
How do you do it? I think you need to move away from thinking a sermon needs every sentence mapped out, and instead think in bigger blocks. If you know your material well, you could speak impromptu on this or that element. So why not thw whole thing? I think that's the best way to approach it.
Con is starting to like preaching without notes
