It's actually easy, people just over-think the heck out of it. There's many ways to get into 'mixed voice'. If you need more help, contact me at my website: www.rachelgerrard.com
What the hell does mixed voice mean to you? No, really, mixed voice (if you're talking about the combination of TA & CT engagement simultaneously, then it should not exist according to all the several Otorhinolaryngologists I talked to). If you're talking about a resonance thing, well that's a whole different story...