Voice Training

Right so I've been living full time for nigh on 10 years now and recently got an appointment for a voice operation (after a referral from O'Shey 6 odd months ago) and I want to do some ground work before the appointment. I tried speech therapy a long time ago but it didn't do anything for me because the thing is that for some reason whenever I was talking to someone I know I'd automatically revert back to my male voice and then find it hard to get out of it again (silly I know but's it's probably some psychological crap I assume).

Anyway I want to try again and do it on my own this time instead of paying a therapist and I know I could google any amount of "Guides" but, like a lot of "TS Guides" , not all are worth bothering with so I was wondering if any one has any they could recommend from personal experience of success with them? Now just to be clear my voice isn't terribly deep or anything and I do have limited, short term control where I can get a somewhat passable few sentences out before the timber starts to kick in again (I'm hoping the voice operation will help with that) so what I'd be looking for is something (sites, youtubes) that can show some muscle exercise techniques if any of that makes sense.