Power shifting is shifting while rolling without using the clutch. You have to match the engine rpm to the speed your traveling to get the gears to line up enough to slip into gear.
All standard trans I have ever seen have a inspection cover. If it's a stuck throwout bearing, it can stick with the clutch engaged, or disengaged. The tree truck last year was stuck engaged, therefore it was always in gear. So I power shifted it to drive it home.
If yours is stuck in the disengaged position, I would crawl under the bus with the bus shut off. Use a pry bar through the inspection hole to manually force the clutch disk forward to it makes contact with the pressure plate again.
Then jump in the bus, stick it in first, and don't touch the clutch. Try to start the bus. It should jump forward as soon as the starter starts spinning. Then start driving and power shift your way home.
Throwout bearings are like everything else. They sit to long they sometimes stick. They live in a vary harsh environment under there. Oil, mud, water, and clutch disk material gum them up.
"Don't argue with stupid people. They will just drag you down to their level, and beat you up with experience."
Patently waiting for the apocalypses to level the playing field in this physiological game of life commonly known as Civilization