Hi Panlei, try this technique...
Here's what I do and it works great and couldn't be easier. Take the poly fill out. Cut it down into three pieces. Take your liquid and fill the cart. I can usually get anywhere between 10-13 drops in there. That should take you to just below the 'neck'. (Where the cart goes into the atty)
Then, take one of the little pieces of polyfill and pop it on the top there. Don't push it in, just sit it on the top, maybe about 1mm down from the edge, if you need that much. Just make sure the threads aren't going to go in the atty or you'll get that nasty 'burnt hair' taste and a harsh throat hit. Then, give the stuffing a few drops to wet it, pop it on the atty and you're off!
It DOESN'T flood the atty and it doesn't leak and no, I don't know why not.
(And yes, I'm lazy today and just copied and pasted my response because I just wrote this for someone else. Comments to yourselves gentlemen..

)