If I'm not feeling too lazy to clean cartos then:
I blow out as much residual nicquid as possible,
Soak the cartos overnight in warm water with a couple of Polident Overnight Whitening denture cleaning tablets (NON-mint). Quite awhile ago, folks were having a lot of success with removing carbon from their atomizers by soaking in Polident. It worked well on my 510's atomizers then, so I figured I'd try it on cartos.
After the overnight soak, I syringe flush with clean hot water, blow out as much as possible,
And then dry them. That can be done by propping them up in sunny window for two or
three days - on a tilt, so that you can get airflow on either end. Or, you can use a food dehydrator if ya have one. Some folks bake 'em. I've never tried that, so I can't offer an opinion.