Thanks, OpheliaBlue!
I really though that to do WBTB I had to get out of bed.
And in the couple of weeks I've been in the Intro Class I've realized I do wake up naturally sometimes, even though I'm a deep sleeper. Actually having a light sleeper bed partner has a clear benefit, that is, even if she tries to be careful, from time to time she will wake me up during the night, so that's a chance to try WBTB.
I have to say it is difficult for me to wake up, and stay awake to do incubations, MILD, etc without falling asleep quickly, but I guess is a matter of focus and effort.
No one said WBTB was going to be easy!!