The difference between preaching open air and preaching in a church building is like the difference between cleaning your teeth with a toothpick and a toothbrush.

Open air has to be to the point, single-pointed, and without the fluff of elaborate details about the text. Open air audiences are not as forgiving as church folk. I'm learning it's more effective to use no notes so that you can grab their attention with constant eye contact. You also cannot assume your audience understands Christian lingo like "redemption," "sanctification," or even "repentance" without very clear and simple definitions. If inhouse preaching starts like a steam engine, slow and sure, open air has to start like a racecar, fast and furious. The audience won't give you five minutes to get to your point.

Open air preaching is more the way Spurgeon preached even though he did very little open air. He'd take one verse and elaborate, illustrate, and linedrive. His notes were incredibly sparse. That's very different than going through an eight verse passage and unpacking every detail.