I tried a similar scheme recently. It is not painful because olanzapine puts you to sleep, yes. But it will not lead to СТВ. And yes, you will most likely wake up in a hospital. They will put you into a medically induced coma, hook you up to air tubes. And whether you want it or not, they will treat you. After the tubes, you will most likely have double pneumonia (in addition to intoxication). Imagine how difficult the rehabilitation period will be. You will have to learn to walk, breathe, eat and do basics. You won't be able to wash yourself!
NB! In my country, the law requires medical professionals to send patients to state mental hospitals after an attempt. The conditions there are not the best, believe me, I only recently got out. So do a fact check, find out how the law works in your country.
That's my experience. And it's all because I chose the wrong method. So, think again. Learn from others' mistakes. I understand why you choose the easiest way to CTB, but think better. Really. Do you need this walk of shame?