As a last resort, you could try soaking your cartos in the highest level of Vodka you can find (not flavored) for about an hour or so, then boil them for at least 15 minutes in water. If the water turns brown, change it and repeat. Let the cartos cool, blow them out and stuff a small bit of paper towel into the end where the filter material is. Let them dry overnight. Then refill using the condom method, top off after 15 minutes of letting them sit, and
vape away.
I have been using the same cartos from Smokless Image for three months. I clean mine every week like I said above.
If all else fails, you can remove the filler with a sewing needle by carefully inserting the needle around the center post until it is free, then pick at the filler at the outside edge to pull it out, leaving the center post. You can now use the carto as a pure drip to test flavors. A few drips into the carto (without filler), and vape. You will only get maybe 10 drags before needing to drip again, but it is an acceptable method of testing
juice, especially if you DIY.