Train toilets are locked in stations - plan ahead for these long stops!
Russia/Mongolia - 6 hours
It took four hours to get out of Russia. Passports were collected and taken to an office. Passengers were free to wander off the station to sample the delights of the town of Naushki. Toilets on station not used by us but reported by fellow passengers as very clean (charge). Whole train thoroughly searched inside and out by both Customs and Immigrations. Two of our suitcases were opened by Customs.
Eventually we moved on ten miles across the border (stop for external examination by Mongolian army) to the Mongolian border town of Suche Bator. Passports again collected but Mongolian officials relatively laid back. Nevertheless getting into Mongolia took two hours.
Getting out of Mongolia was comparatively easy, just one hour at Dzamyn Ude then a few minutes to the Chinese frontier at Erlian where the fun begins and we spent over five hours.
After passport collection the train is shunted out of the station, split, and then propelled into a shed. Here the coaches are uncoupled and jacked up. Russian/Mongolian guage bogies are rolled out and the standard guage bogies for China rolled in. The coaches are then lowered onto the bogies, recoupled and taken back to the station. Eventually Customs and Immigration arrived, processed us and left.
We had read that others had been allowed off the train at Erlian until it returned after the bogie change. However on this evening nobody left the train. Whether it was actually forbidden we don't know, but suspect it was.
We had been told that the Torugart Pass frontier could be very busy, especially with lorries, but we saw virtually no traffic on the way apart from one other couple.
First stop is the entrance to the border area about one hour from Kashgar. Here our bags were scanned and we were seen by a medic who took our temperatures. Passports and visas were checked. A rather officious Customs official wanted to see any books that we had. (We had heard reports of books being searched for pictures of the Dalai Lama, maps showing Taiwan in a different colour to Mainland China etc. Quite why this was being done going out when no interest had been shown on our arrival in the country escaped us.)
Our passports were inspected again. As we went out into the compound to the car a passing soldier wanted to see our passports (we think he was bored, or after promotion, or both). We had to show our passports to get out of the compound.
A few miles down the road is another checkpoint, apparently belonging to military police. Passports again.
A bit further on the road enters a village in an autonymous Kyrgyz region of Xinjiang. A makeshift barrier there barred our progress until driver and guide had shown their passes for this area. After that it was plain sailing until the actual Chinese frontier where there is a simple barrier. Here we had to wait until our Kyrgyz driver and guide arrived. This is a sensitive area and waving cameras around would not have been a good idea.
From the frontier to the Kyrgyz border post is about 30 minutes drive (more if you have a puncture, which we did). Kyrgyz Immigration was thorough and efficient. Customs were closed for lunch so we just walked through. A visit to the toilet block was needed, but regretted!