At work at Art's Cyclery, everyone was always struggling and complaining about having to install Cush Core tire inserts. Work times of half an hour or more per wheel were common. Sometimes with up to three people on the job. I finally installed my first set yesterday and found it rather easy. If you just go to the website and watch their how to videos, they really explain it all rather simply. My first one was way quicker than I thought, so I timed myself on the second wheel and did it in just twelve minutes. Even with reduced hand strength due to my MS.
This video... https://www.youtube.com/results?search_query=ali+clarkson+cushcore helps demonstrate how not just pushing down, but down and in towards the rim on the bead is the key.