ctrl v (visual mode) -> highlight lines you want to change -> shift i -> add whatever you want to the line -> escape -> Gets applied to all highlighted lines.

ctrl v (visual mode) -> highlight lines you want to change -> shift i -> add whatever you want to the line -> escape -> Gets applied to all highlighted lines. Surprised at how many vim users I run into don't seem to use visual mode that often, stuff like this is fantastic for commenting out multiple lines at once or aligning "=" signs in stuff like terraform.