I like to consider myself an "expert" of sampling flavors and this is what I do.
When I'm swapping flavors (review not involved) I don't use a cartridge. I use blank mouthpieces and clean both the mouthpiece and the atomizer.
Before any reviews I do I give my mouthpieces and atomizers a full, deep-cleaning. I rinse them, blow them out, boil them, blow them out, rinse them again, blow them out and then let them dry. After that I hook them up to a battery and cook any left-over water out of them. This way, there is no chance for any residual flavor contaminating the sample I am reviewing. Once all of this is done I make a new cartridge with fresh batting and prime the atomizer with the flavor I am reviewing and let it sit for several minutes before starting the review.
I never use anything that's been exposed to another flavor unless it's been very thoroughly cleaned out.
I even swab out my batteries
For personal samplings, clean your atomizer and drip. That'll be fine.
