Sure, there are all kinds of methods for carto cleaning. I'm sure some will post theirs, but a search of the forum for "cleaning cartomizer" should turn up a bunch ;-)
I DIY most of my juices at either 50% VG or all VG and haven't really had any trouble with the draw changing on tanked cartomizers, however I have noticed some cartos just generally draw stiffer than others (even if they're the same brand). Try looking down the center of your carto and if you cant see all the way
through you can
carefully run a pin or straightened paper clip
through to try and straighten out the center tube. Sometimes I've had this collapse on me after a lot of use or after cleaning and that will tighten up the draw quite a bit