My understanding is that it is common to start with laser, then move to electrolysis. If laser has dealt with the majority of hairs, is the electrolysis tech able to "ignore" those follicles? If not, starting with laser seems pointless.
I have been doing laser for a while but am starting to think electrolysis will be necessary prior to surgery for some of the finer hairs.

Electrolysis works by literally inserting a needle where you want to destroy the hair follicles. So you would only use it on the remaining hair, yes. It also hurts like hell compared to laser. and since they're zapping each hair individually it also takes a lot longer. Do laser first, if some hairs remain go for electrolysis.

Depends on the surgery. If it's for bottom surgery then yes, electrolysis will be necessary. Your surgeon should give you clear instructions about where and how they require hair removal.

I heard some surgeon use a chemical based permanent hair removal on the inverted part of skin tissue. But I just heard it second hand.

My surgeon said they could do electrolysis on the remaining hairs when I was under general anaesthetic

I have not heard that but the surgeon I went to did offer hip skin grafts if someone was not wanting to do electrolysis as that skin is hair free on most people.

They did, yes. I just wasn't sure if the electrolysis tech would be able to tell if a hair follicle was dealt with already or if they would have to do each one regardless of whether hair remained.

It's for hairs whose coloration isn't dark enough to accumulate/absorb enough heat (70°C) from the laser in order for them to be incinerated. I'm currently doing belly, chest and face and - goddammit - I have two patches, one on each side of my face, just below my ears, that are white like snow... I'm going to have to do electrolysis ("diathermy" in my language). My threshold for pain is so low, that I need to apply morphine cream on my face at least half an hour before she zaps my face, so I can't even image what the electrolysis is going to feel like 😅 as long as she does it, I don't mind though. I'm not a masochist, I just adore her. 🩷

Electrologists have you grow the hair on the target area out for a day or two before the appointment so they can see where the hairs are. For genital hair the best approach is to not shave but trim the hair short the day before (use a guard on the trimmers!!). That ensures any hair that can still grow will have the best possible chance to be spotted. You'll probably have appointments on a weekly or bi-weekly basis over the course of several months so it's unlikely that one would slip through.