I've found that the "drip and shake" method works for me.
First, I put a wooden toothpic part way into the center air hole to keep out unwanted juice. This totally eliminates the need to blow on the tank and taste e-liquid. Yuk!
Then I drip my juice into the cart's filler until it looks saturated. I then shake the carto like a thermometer a few times. This replicates a centrifuge action. I add more liquid, shake a few times. I continue this ritual a couple more times until the carto will hold no more juice. Remove the tooth pick, and add a tank accessory tool to put the carto half way into the tank and fill it up.
Once the tank is 80% full, I push the cart the rest of the way into the tank, remove the tank tool and add a drip tip, and ready to vape immediately.
No need to blow through the air hole. No need to let the tank "sit". The entire process takes 5 minutes.
http://www.e-cigarette-forum.com/forum/blogs/baditude/3710-5-cartomizer-tank-setup.html