The best method is the one you have very well researched, and you are comfortable with and can see yourself doing, including overcoming SI.
If you have looked into iron overdosing, and you like what you read and the side effect it comes with, and the chances of success (all of these need the research part), then go for it. For me, who has done very limited research on the method and knows a fair bit about physiology, I would not take this method, but if you have done your research and accept all the eventualities and outcomes, then this is your way to go.
I know for example that jumping is a very sure way if done from a high enough place with a hard enough ground, but I can't even jump from 2 steps of a ladder because I'm scared of heights, so no matter what, jumping will not be my way to go.
I think to find your method you need to consider 4 things:
1. Research: What can be done, what are the chances, side effects, time line
2. Availability: What can you get, how long will it take, how much will it cost
3. Opportunity: How much time are you willing to die, how much time do you get alone to carry it out, what requirements does your method have to your environment
4. SI: What are you naturally afraid of, can you imagine yourself overcoming it, are you willing to practice and visualize to get more comfortable with what you need to do
There might be more, but that is what my tried brain can offer right now.