Here is a really good article from Faster Skier on the source of speed on skis. Talks about rapid force development. And keeping the resulting total volume of force high—even if you shorten the cycle with higher tempo.
Always keep in mind that the pole angles and ski angles need to be correct before you apply force to them. Planting a vertical pole then hitting it hard with all your body weight and trunk force will just beat you up—not make you go faster. Plant it with a back angle and hit it hard/fast and you will go faster!! Standing on a straight leg then doing a little shallow dip preload will not be nearly as powerful as dropping further to gain more angle at the ankle/knee to use during the extension in the push. Just do as fast a reversal as you can at the bottom for the preload!! Then snap it all the way out!! If you push across low—you can use those entire compressed angles—but do it quickly!!
Also be cautious with the plyos as shown in the video clips. Start easy after a good warmup. And, as the article says, if you are beyond just sore the next day—take more than one day before you do it again, and if necessary, talk to a sports trainer.