Here is a playlist link to a solo walkthrough of Gears 4 on Insane. It is broken up into chapters and has commentary throughout.
https://www.youtube.com/playlist?list=PLTaOHX8kEkD7UVdDf2Gnx...If you are not a fan of commentated strategy videos then here is a link to full walkthrough of the game without.
https://www.youtube.com/playlist?list=PLTaOHX8kEkD6pkUxA8N69...Hope this helps.