Having seen this several times in family and close relatives it does not appear as painful as you'd think. Often times the people responsible for the care of the person dying will provide them small amounts of water, typically via a syringe, to keep their mouth wet in order to not provoke a thirst response. Food is easy enough to ignore and most people can indefinitely ignore hunger right up until they die.

It seems clear to me you have never seen this procedure done. It was rather traumatic for me having to be one of the people responsible for the final caregiving (it does not seem logical to provide such comforts as small water or medicine to someone committed to dying) but it was important for closure. I hope you dont have to witness it or make this choice yourself.

Personally, I find doctor assisted suicide to be both unethical and amoral. While people may disagree with me I see no difference between MAID and paying someone to hang you as instantaneous death is guaranteed in both ways and it is done by a sanctioned murderer. VSED is entirely in the dying person's control, and thus to me is not unethical nor amoral as the control of life is in the person who owns that life.