I cut a short length of extrusion, inserted a piece of truss-pole stock part way into it, and epoxyed it in place, making a socket into which another piece of truss pole would fit. Beeswax made the slip fit into a stiff joint that was entirely satisfactory for the telescope. It is not necessary to fill the space between pole and extrusion with beeswax. A little will do, and once there is some there, you don't necessarily need to keep adding more every time you assemble the poles. I do this part of assembly and dissembly in a motel room.
Beeswax softens enough under a hot water faucet to make the task easy.
I carry a little plastic bottle of spare beeswax, that I can melt entirely by putting it in a glass filled with boiling water from my portable coffee heater. That way I can add more beeswax if necessary. With that trick in mind, I went ahead with my project.