It took me two months and 250 miles to become confident with shifting my '52 2-ton. I depress the clutch pedal to pull it out of 1st gear, but the stick will rarely shift into 2nd until I let the clutch out - then it drops in smoothly. Second to 3rd is a normal shift. Shifting from 3rd to 4th requires a double-clutch. I can downshift from 4th to 3rd without needing a double-clutch. Downshifting from 3rd to 2nd can only be done at a very slow ground speed.
My two young sons still cover their ears when I shift - they don't like the "scary" sound when it grinds. They've asked if our truck is "broken"!