To be honest, I don't clean my atomizers. At most - I'll blow them out thoroughly and reprime. That being said, there are several ways that others clean them. The most common is... hot water rinse and dry burn. Followed by soaking in alcohol for X amount of time. If I were to recommend either of them, I would recommend soaking them in vodka for 30 minutes, lightly move the atomizer around to break free any stuck particles, and soak for another 30 minutes. Dry burning may work, but can dramatically shorten the life of your atomizer by causing the coil to stretch/warp/come in contact with other parts of the coil causing a short and also weaken solder/adhesive points.
Think I'll stick to blowing.