If I want diffusion, I prefer to use a classic portrait lens (Verito, Heliar, Petzval) and large format, but David Mullen gives an excellent taxonomy of diffusion filters here--

http://www.cinematography.com/index.php?showtopic=42112

Other ways to smooth out wrinkles are softening the light, increasing the fill in relation to the main light, and retouching the neg of course.