Use WARM water, and soap, and get one of those small brushed they have for cleaning baby bottles, the really small ones. Wash the parts inside and out, let them dry completely. If you want to speed up the process, use q-tips to get the nooks and crannies.
Reassemble, and prime the head with the juice you intend to use - a couple of drops on either side on the wick should do it. Finish assembly, fill tank. You should get a lot less gurgling. Or, just let it sit for a while before you use it. I've found gurgling is usually from an unprimed wick, or a wick that's clogged on one side.
As for lingering flavor, the mints tend to be clingy, so you have to really look for places it can creep into - threads, under the silicon gasket on the head, inside the head, in the drip tip - a really good thorough cleaning and a new head should get rid of it, along with a coil burn if you don't replace the head.