Jump the next train
Before I left for this trip, I tried quite hard to get some information of what I should pack. Inner Siberia being one of the more tricky places to know what temperature it will be, and my experience was exactly that. When we arrived in Irkutsk it was 31 degrees, but it dropped to 2 at night.
On the train it was more than hot enough to just wear some loose pants, and several even used shorts.
Another part I had trouble getting information about was how much money I would need for these days, as you can only use cash on the train, and there is (of course) no ATM.
My experience here is that you really do not need a lot. Bring a cup to warm noodles from home, buy a few different packs of noodels before you get on the train and possibly a bottle of water. There is hot water in all wagons. Water is sold in the resturant wagon, they hold a massive menu for food as well, but barely have any of the items on the menu. What they do have was however excellent soups and some very doable meals, including some kind of meatpies which were delicious.
Depending on how many days you have to stay on the train before stopping in a city with an ATM, it will most likely be more than enough to get $10 per day, and that should also include some beers as well.
With the group having two full four persons compartments, as well as 3/4 of two others, I ended up in one with two girls from England as well as a Russian lady who didn't know any english, and from what it seemed when the attendant tried to talk to her, she didn't really speak much russian either. In short, all she did on the almost 4 days we spent together was sit and rub her arm or face, sleep or stand in the hallway looking out the window. I did however set myself up for a tricky task of high-fiving her before she left us, and somehow managed to succeed with that after I helped her off at her stop.
The train stops quite often, but most stops are 1-2 minutes and you are not allowed to go out on those. There are longer stops, usually 20-60mins about every 4-5th hour, both day and night. You may leave the train, but it's completely up to yourself to get back on before it leaves. There is no signal, but it's really not difficult to get back on, and you can just get on any wagon and walk back to your own while in motion.
I'd expected the 88 hours from Moscow to Irkutsk to become a bit boring, but with the group we were able to keep ourselves active quite well. Did manage to read through most of my book, but it was much less boring than expected. I'd also brought with me my quiz-sheet where I adapted it to international-version and ran a quiz just before or after dinner every day on the train. Everyone joined in, but if that was for lack of options or because it was awesome is a bit more uncertain.
In the resturant wagon there was a few russians who drank more or less the whole trip, but that was probably as expected. They were friendly enough, but after quite a lot of beers they did get quite pushy on the girls - possibly because they aren't as rough at dismissing them as the locals.
With the train running on Moscow-time the whole way, but with us crossing 5 timezones in 4 days, it meant that most of our days were 22-23 hours, and with keeping our watches at Moscow-time, it also meant that we had to get up at 4am which could mean 8-9 and get to bed at 19 which was really 23. In addition to this we didn't really spend much (any) energy, so when to eat or how much got a bit messed up as well. I would guess taking the train the other way would be easier, and if I do this trip again some day, that is what I'm going to do.
