I've not tried cleaning the cartos with alcohol -- any kind, but I did try the boiling method. I took off the little rings on the top and the one inside, and put the cartos in a pot of water and boiled them. I don't remember how long it was now, but I got the instructions here on ECF. Took a couple of days for them to dry. I probably could have dried them more quickly with a blow dryer.
Anyway, they were like you are describing. Didn't appear to have been cleaned at all. Almost impossible to fill, nearly impossible to draw on. I was seriously ready to abandon the idea of cartos and toss them.
The other day here on ECF, I read to remove the rings, then hold them, battery end down, under hot running water for several minutes, then blow out the water from the battery end, and let them dry the rest of the way. Being the type who doesn't have much patience with fiddly things, I banded a bunch together, 8 or 9, with a thick rubber band. I used my Serger tweezers to hold them under the hot water, but you could use kitchen tongs, too. Since there is nothing in them but water, probably could use them again as soon as they are to the "damp" stage, but I did let mine dry completely.
The filler washed out just as nice and white as the day I got them out of the package. They fill beautifully, and work like new. Give the hot water treatment a shot. Worked for me.
I also stopped putting those little rings (inside one and end one) back on them. Nuisance!! I fill them from the top with the carto at an angle, and holding onto the top end I give the carto a few shakes, like shaking down a thermometer. I tried the condom method, but this works better for me.
I have been vapping regularly now for a few weeks and I am using a Red Dragon (E9) I attempted to refill the prefilled cartomizers. After I did they were really hard to draw on, so I cleaned them out with alcohol, thoroughly dried them out and tested them for draw. They are still very hard to draw on. So what did I do wrong. 
