I have read a bit about it and it does seem to take quite a long time. Even up to 24 hours seems a long time to me. If you're knocked out everything is fine, if not it might not be such a peaceful way to die.
If it's too many pills for some, you can also get it in liquid form. Suppose it will have the same effect.
I strongly advise you not to try it without a long-acting Benzo! Seizures, organ failure etc is nothing I want to experience while conscious.....
Amitriptilyne, Trimipramine, Doxepine etc. Should all be fine.