I have small children in the house and was nervous about having needles, blundt or otherwise, in the house. So I use a paperclip to push through the hole in the cart to get the inside cart out. From there simply use the paperclip to get the stuffing out, roll the stuffing in paper towel to get the juice out or clean it with hot water and dry, then use a Q-tip to clean out any xtra juice in the empty cart.
With all that completed you can then drop liquid into the empty cart, put the stuffing back in, use the paperclip to push down the stuffing and get it nice and wet, put a few more drops of liquid in, then squish around again and pull the stuffing back up so it makes contact with the atomizer.
If you do tend to change flavors of liquids alot, as I do..make sure you blow out your atomizer when you change carts. Otherwise you might really despise the flavor combination you've made since there is still juice in the atomizer.
Spikey has a GREAT video on how to refill carts. It's worth watching.