I recommend reading the PPH:
https://sanctioned-suicide.net/threads/peaceful-pill-ehandbook-2020.35699/
SN (sodium nitrite) is a great method. Depending on which part of the world you are you may be able to buy chloroquine or amytriptyline which are reliable drugs to CTB. N (nembutal) is perfect but hard and expensive to get.
A very reliable method which do not involve drugs is the exit bag.
Check the PPH for a list of methods and the forums for more information.