A long enough spoke, or two of them joined with a nipple in the center, might act as a good cleaning rod. Or you can make yourself a pull-cleaner from skinny cable, like shifter cable, with a loop on the end joined with a small crimp connector (or a running eye splice if you happen to be good at that on twisted cable or rope), and that should be stiff enough to shove through the tube, put a small cleaning patch through the loop, pull back thru.

Normally you "can't push on a rope" or cable, but if constrained enough laterally in a tube, you can, at least just for pushing the small end through, before adding friction with a cleaning patch to pull through.