Great question! There are multiple approaches to counter sloth, as indicated in the article. Sloth and torpor are essentially an imbalance of energy, being on the lower end of the energy spectrum. The ideas for counters are naturally those things that arose energy of the sort that will refresh and buoy the mind. The goal isn't to swing as a pendulum from one extreme to the other, but to slowly bring it to the center - perfectly balanced between relaxation and excitement.
Wise attention is keeping something's origin in mind, seeing to know the causal relationships, and to pay attention to arising phenomena in such a way as to understand clearly their true nature - impermanent, unsatisfying, and Not-Self. Wise attention is the dawn, the forerunner of the Noble Eightfold Path. So, watch the hindrances thusly - observe so as to know their conditioned origin, know how they arise and fall, know that they are impermanent, not you, and are indeed unsatisfying.
Inspiring topics can counter sloth, but the topic should be one that directs you toward balance, toward the Dhamma, toward peace and relinquishment. Battle speeches may be inspiring, but may also over agitate the mind and inspire wandering thoughts. I find good Dhamma talks or books can be very inspiring in the right doses, and invigorate a slothful mind. On long retreats, one may get quite exhausted at times - but a good Dhamma talk can be like the strong arm of a good friend pulling you back up to your feet.
Experiences of awe, being moved, wonder, etc. also can work, if treated with wise attention and bring one to balance. They can be over-stimulating and lead to restlessness as well. For example, if you have an amazing meditative experience, have some nimitta or bright lights of joy or Piti, one may feel awe, moved to tears, and then firmly attach, cling, and identify with these experiences. But with wise attention, we are not trapped by such, and let those go too. They can be motivating - if it gets us on the cushion for the right reason, great. It shouldn't be to replicate those feelings or recreate experience or attain something specific though.