Isopropyl alcohol had been mentioned a couple times, but that's what I use. Everywhere on the Internet I see says to dilute it, because it might hurt some if your more sensitive plants, but I never do. A, I've not yet found a plant sensitive enough to care, though I've not tried it on my flytrap yet. The pitcher plant didn't care, neither did my citrus trees when I had them. And B, I figured at this point, either I'm going to kill them trying to kill off the infestation, the infestation is going to kill them, or I'm going to dispose of the plant before the rest of my indoor jungle is infested. I put it in a spray bottle and spray the whole plant until it's dripping off. I would try to avoid so much that it's dripping into the pot, maybe turn it sideways like someone suggested with the soap.
First though, go through and manually remove every one of the scale bugs you can find, pay close attention to the undersides of leaves and to joints. If you have a particular heavily invested spot, consider if the plant can stand to have that spot removed entirely. As someone else mentioned, they lay eggs. If you remove the branch, eggs and all are gone. I would either incinerate or garbage the clippings, rather than risk contaminating my compost.
Also, if you haven't already, inspect every plant nearby. If you have a heavy enough investigation, and it sounds like you do, these videos will spread from the initial host to whatever is nearby. They are much easier to deal with when they're just a few of them.
Also, again because of the eggs, you'll have to keep going back every day or three and play the removal game again, until you manage to kill the very last one from the very last egg. This will probably take the better part of a month to get the last, though total number of the pests should drop of fairly sharply.
