Afraid there are no tricks here... you need to make good, watchable, shareable and bingeable content. If you use the tools provided by TubeBuddy to master your CTR and SEO you are going to get in front of viewers. When you are able to keep those viewers around and get them to start watching multiple videos your watchtime will come (and easier than you think).
FYI For our channel I managed to hit the 4k watchtime requirement after about 8 months... and ALL of that came from a single video that happened to perform really well over that time frame. So the good news is that it only takes one video to make it happen!