How do you shift a 18 speed transmission?

The shift pattern is a modified nine speed transmission, with the option to split the gears via the button on the side. To upshift with the splitter, you get up to the desired RPMs, push the splitter button forward, let off the accelerator for a second or two, then get back on the accelerator. If you did it right, you'll proceed as normal. If you get back on the accelerator too soon, the motor will tack up very high and very quickly once you get back on the accelerator, as you'll not have caught the gear yet. You do pretty much the same thing when downshifting.

As for the progressive shift motions, if you're familiar with unsynchronised transmissions, the pattern is basically that of a nine speed. If you don't know how to shift one, you need to learn - either have someone teach you, or attend a truck driving school.