Trim Wallpaper Along the Curvature of an Arch - Spencer Colgan 

Your the master that inspires, I can’t take your sarcasm seriously. To funny.

I use my 6” blade as the backing and cut along the edge of the arch and down the wall. I don’t think I would do it like this.

Looks alright from a distance not close up cutting in very rough

do u have videos on painting windows?

I suggest that you paint the arch before papering, come up with a better guide to draw your pencil line and use a very light pencil to mark your cutting line. You are welcome.