I did the lasing and now am doing the electro. Never used/use pain killers. I just cry tears of joy. Good times. Good times....ugh.
I will say, that much like you, my hair was part white/grey and part dark. So, the laser took care of most of the dark. However, as I am now doing just electro, and I have to grow it out for that, I see black hairs every time I grow it out. Not just a couple, either, dammit. So, what I am telling you is that laser is not 100% permanent. It will kill a lot, and lessen the regrowth, but depending on growth stages when you get zapped, it may not permanently remove that hair. Don't get me wrong, lasing did get rid most of my growth --and quickly, but electro is the only permanent solution. 😉