Just tonight I learned the value of cleaning my atty between flavors. If I didn't clean my atty, the tastes of everything I vaped before were all present in the taste, and let me say that it can get quite disgusting and absolutely ruins the taste of any new flavor you might try to use.
Here is what i did that worked wonders, its relatively quick and doesn't require anything too out of the ordinary.
I simply got one of my Arrowhead water bottles (1 pint), grabbed a knife, and jammed it into the cap and turned. What this did was open up a small hole, small enough for me to stick the .... end of my atty in (the screw portion with the majority of the atty sticking out above the cap). It was far from being a total seal, but that didn't matter. Ideally you could just drill it out to roughly the size of your atty threads, but my drills battery was dead, so I improvised.
Then I just got hot tap water (from the faucet) and squeezed the bottle of hot water through the atty once or twice (twice seems to be acceptably good).
After running the hot water through the atty, I took it out, dried off the outside then grabbed some toilet paper to gather up any residual water from inside the atty (I just wadded up the paper and put it in the atty and blew into it).
After blowing out the majority of the remaining water from the atty, I then dry burned it a few times to further dry it up (at this point you shouldn't see any smoke if the atty is truly clean, should just be warm air you suck in).
After this 95% or more of the flavored juice smell/taste you previously used will be gone, leaving you with a nice fresh atty to use with a new flavor. It takes about 5 minuets (maybe less) and works amazingly well for how simple the procedure is. I'm sure with a more seasoned atty it will require more robust cleaning methods, but my attys are all pretty new, so using this process proved easy to get them clean again.
Hope that helps.
