No cotton needed, The issue is a clog in the air path. Two solutions to your problem come to mind. The first is clearing clogs without holding the button. Unscrew your clogged cart and pull on it like you were taking a hit and try to pop the clog free that way. When you have a clog and hold the button to melt it pressure builds up and the majority of the load is now liquified and ready to shoot out. The other issue I can see is not cooling down your carts after use. If you have a big session and just set it down you will get a clog every time. After your last hit you want to continue hitting the cart without pressing the button so you can cool the concentrate and cart down to room temperature allowing the concentrate to re solidify without a clog in the flu.