Vcat, you don't need an excuse! Everyone needs their own space and has their own way of doing things. If you don't want them to help, respectfully tell them that you can handle the painting on your own and give them some excuse (make something up, like a fight with a friend, etc.) as to why you want to be by yourself to have time to think.
Oh, and the next time he looks at a personal piece of your anatomy, say what Shannon says, "Really?, Really?"

I've also see her stand and glare at someone who has seriously ticked her off until I am sure I've seen smoke coming from a hole on their chest!

Did I tell you she can be a b***h sometimes and she doesn't smoke?!? I have NO IDEA where she gets that from.