Question regareding Vapor King and the Dual Coil

[allcoast]

I am having an issue with the Vapor King Dual Coil item. When I first use it, it is great. But after a couple refills, the draw gets harder and it feels like it is gunked up. Does anyone know of a way to clean this, or any other ideas? Also, what other dual coil technology could I use the Vapor King Storm battery with? Thanks in advance for the help and guidance.