How do I express these instructions to a user in the most user-friendly way?

Here I have a screen which is intended for the user to search for and outline their yard with a set of tools in the toolbar (The pen and scissor tool is toggled when tapped).

I need to explain the use of each button in the toolbar as well as instruct the user to outline the entirety of their yard with the pen tool and then outline the part of their yard with the scissor tool which is not grass (houses, sheds, driveways, etc.)

What would work best here? Interactive tutorial? A video? How and where do I explain the functions and steps to keep it as simple as possible? I have tried creating a dialog with slides explaining each button's function but didn't really like the outcome. Since I wrote the app, it's really hard knowing if what I write is simple enough and/or user-friendly.