I am planning to make a winter ascent of a 4850 meters mountain which its summit's lowest and chill temperatures are around -30C(-22F) and -40C(-40F), respectively. It takes at least 3 days to reach the summit whilst the grade is D and in some parts TD based on IFAS system.

Right now, I have a pair of winter mountaineering boots which do not have any removable thermal booties. I was wondering how can I use them in this expedition. I have heard form some classic climbers that they used fake wrestling shoes(because the fake ones are cheap) along with wool socks as a removable thermal boot in their boots, in the past. Do you have any better idea(s) ( :) ), that I can apply to my boots regarding this journey?

By the way, I am quite delightful to find this stack exchange website, specifically for outdoor activities with many experts on it :)