It is certainly not the most peaceful method. But, don't despair.
I want to point you to people who have had to suffer so much, and yet they endured it without flinching.
Perhaps most renowned of such examples would be xiaolin monks, who show their incredible concentration and can take tremendous punishment without feeling a thing.
They remind us that all suffering is in the mind. There are those who could endure tremendous suffering for countless extensions of time, without a tear, without a flinch.
All I ask of you, in comparison, is but a few moments. An instant, in the extension of your entire life, and an instant of suffering that you know will lead to your eternal peace.
Sit down, in silence. Meditate. Fast. And focus your mind on knowing what awaits you: peace and happiness.
I believe what causes suffering on such last moments, is no physical pain, but that, as this discomfort creeps in, it confirms you, deep to your core, that it is happening: that you are indeed dying. And if your mind isn't set on it, if you are not absolutely certain that you wanna do this, it is that last moment of doubt that will be the most painful.
But if your mind is set on it, if you are certain, and there is not an inch of doubt on your mind, that you wanna do this, then there is nothing to fear. As this feelings creep in, they won't hurt you, but put you at ease, as they reassure you that your end is coming, and that your passing to the afterlife will come soon.
I hope you don't do this, my friend. For I support life first and foremost and your freedom to decide second. But, should this be it, and your time is coming soon, I don't wish you anything, for I know that only peace and happiness lays ahead of you.
best of luck, my friend.