Altering the background in fcp

So I took some video with a few freinds for a school project. I showed our teacher some of it, and he likes it all, except for in one clip, my friend has a flagpole behind him that looks like it is coming out of his head. Logistically, it would be complicated to meet again, so does anyone know a good way to get rid of it in post? I have final cut studio, the footage is in black and white, and I am trying to figure out how to use the 50 point matte plugin (i thought that maybe I could blur it out and fake a shallow dof at the same time). I am also trying a solution where I have the same video clip at the same time on two tracks, and then masking a small area of just the sky next to the flagpole, then offsetting that video track (like moving the center point in the motion tab), and I am having mixed results (the expected result is happening, but it looks shitty). Should I Just start key framing with the 50 point matte plug in on a duplicate clip at the same time and apply a blur, or does anyone here have a better solution?

thanks