If you have a starter, don't hold your finger over anything. Just turn the engine over with the starter. Fuel will be pulled up into the combustion chamber, and it will fire. The only complication (which really isn't a complication, you just have to allow for it) with starting a cowled engine is the glow driver. If the head is exposed, then just plug in the driver. If the head isn't exposed, then you'll need a remote glow ignitor. If you want to prime your engine, then hold your finger over the exhaust WHILE TURNING THE PROP BY HAND--NOT BY ELECTRIC STARTER. Then, once primed, hit it with the starter. I don't like using this method because of the possibilty of hydrolock, and the starter tearing up my engine. But, that's my preference.

Edit:

Make sure the glow driver isn't plugged in if you are priming it by hand! [X(]