Sometimes you have to wonder if the stars and starlets shilling products on-screen actually use the stuff in real life. But not in this case. Procter & Gamble Co. has signed TV star Jesse Tyler Ferguson, who plays the neat freak character Mitchell Pritchett on “Modern Family,” to push Swiffer sweepers and Febreze fabric refresher.   Ferguson said his role on the ABC show isn’t a stretch because much of Mitch is based on his own idiosyncrasies.   “Everyone knows I’m a neat freak,...