I've tried all kinds of tricks to clean a cartomizer. None were worth the effort. Just pitch 'em when they're done. Try to avoid changing flavors and don't let them dry out while firing them. Everything else I've tried was a waste of time, juice, and money.
I've only used the CE2's in the clearomizer style. Major PITA - leaks, slow wicking, cracking tubes. Nothing like screwing up a new cartomizer, wasting juice, and having a mess all over your PV and work area. I have a couple of versions of the newer tank mods that are out now, but I don't expect them to last long before the rubber end-plugs start deteriorating. If I can make use of the CE2's I have on-hand, I won't consider it a loss. Another passing fad. They were cleanable though.
I'm content reverting back to high quality cartos like Boge's and Ikenvapes. When they wear out - well, they are considered disposable... I've had them last over six weeks with no taste change. I don't have time to keep tinkering with stuff that doesn't work or is wornout.