You have to clean it in order to change juices and not have any trace of the previous juice. I keep many attys on standby, and to clean them, I soak them in alcohol for 12-24 hours. Then I boil then in distilled water for about 20 min to remove the alcohol. Then I let them air dry in a tin I have. That way, I have them ready and grab one as needed. Its the best system for me that I have found.
I have 4 tanks, and like 10 attys so I never have to wait for one to dry. I dont like waiting or not being able to vape when I want to. Ive tried to tweek my system so I have standbys for my standbys.