I would say to hold off on clutch-less shifting for a while, and in response to OP's last question about staying in the gas during a shift, remember that a duece is not a Porsche. You're not worried about your time at the drag strip, right? Like has been said previously, a see-saw action is appropriate, and it is acceptable to be moving your right foot to get your revs matched up while your left foot is moving up off the clutch. If you choose to throttle while releasing the clutch, your goal should be smoothness of operation. When you're shifting through the gears, it should like like a work of art, your truck should be so smooth. No jerking, no gear-grinding. This holds true for accelerating and slowing down to a full stop. Take a couple hours out in the country to just practice this, take your time, and focus on smoothness. You'll thank yourself later, because your reward will be that you make driving the duece "look good" to everyone else.
I believe the manuals advise against double-clutching, if I'm wrong on this point I'm sure others will correct me. Furthermore, I believe the manuals also advise against down-shifting in 1st, 2nd, and 3rd. So you're supposed to use your brakes to slow down to a stop, instead of letting the transmission and clutch take the wear and tear of the stop.