I have never had any luck rooting these, sadly.

http://kumbulanursery.co.za/plants/senecio-haworthii
That says tip cuttings in the Spring will root. I can't wait that long.

Your stems are thick enough that it should root if the plant is up for it.

Cut the stems up to the last leaves on each set. Pull off said last leaves, both of them. Let the cut callus for a day in open air.

Then stick them in your mix to above the area you removed the two leaves, preferably in very gritty mix. I like laying half the pot down with mix, watering that in, then filling the top half of the pot with dry mix, and ensuring the cuttings go in the dry part.

Then let completely dry until they're rooted, or at best, dunk the bottom half of the pot in water occasionally. (This only works if you have a very gritty mix and not something like peat which will suck up water to the top, in which case do not water but spritz from the top after 7-10 days or so.)

Keep them in bright light but indirect sun. It usually takes 2-3 weeks in warm weather, so be patient. I've never had stems so long so I'm not sure if the stems roots on their own with the tips cut off, though I see no reason they wouldn't. With these, I only root the stubbiest tip cuttings, with stems short and compact as they were taken off a main live plant. If I had to bet, the tallest one, once it's cut down, will root, but not sure about the others as they're in significantly poorer condition, it looks like.