Just an FYI that this idea is not going to work.
I gave it a go on one of the armchair covers and it turned out like this:
Looks like I spilled Kool-Aid on it....
I think this project probably works alot better when starting with a lighter color fabric and painting it a darker color. If I wanted to paint the chair black, I'm sure it would work. But.... I don't want to paint it black. So I am kind of back to square one on what to do with the wingback.
I will report back with any more ideas.