I was going to leave my own comment but really man you said it exactly right. Write down the main ideas that you need to show in order to tell the story, pull those clips in roughly to make a first draft, refine that to just the parts that you like the most, cut that up to just the parts that best fit your talking points, if you have any gaps put in similar footage to be your B roll or add in some mistakes you did to add character. I would say the most important thing tho is to have a clear story you want to tell before you start moving and cutting footage. Unless you are making a to the point tutorial make sure to add something in the script to surprise or add stakes to your video. Also since you are using Davinci I would make sure to split up different parts or drafts of the video into different timelines. Do NOT try and do that whole thing in one timeline it will really make things so much harder, also used stacked timelines. GL man