Old Sub's got it right. I learned to split-shift on a Mack B-73 with a 262 Cummins and a TriPlex. 5 speed main box, 3-speed auxiliary. (two shifters) Once the rig is moving, don't use the clutch, just synchronize the RPM. Some of the shifting is done with both hands on the shifters, none on the steering wheel.

Main box in 1st.
Brownie in 1st. Let the clutch out, and forget it's there. Shift the Brownie 1-2-3.
Put main in neutral, shift brownie to 1st. Put main in 2nd.

Shift Brownie 1-2-3. Main in neutral, Brownie to 1st, main to 3rd. etc.!

Downshifting worked just the opposite. A good driver could go up and down 15 speeds, and never use the clutch. When I got a 10-speed Roadranger with an air splitter, I was in hog heaven!
Jerry

"It is better to be silent and be thought a fool than to speak and eliminate all doubt!" - Abraham Lincoln
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