The key to this “Lunar Express” approach is addition of a new component, a logistics module, to the Soyuz. In the strawman mission architecture Anderman outlined in his conference presentation, the logistics module and an upper stage are launched into an ISS orbit by a generic launch vehicle.
...
Once the module and upper stage were in orbit, a Soyuz spacecraft that had completed its half-year stay at the ISS would undock from the station and dock with the logistics module. The upper stage attached to the other end of the logistics module then fires, sending the complete spacecraft on a free-return circumlunar trajectory. The upper stage is jettisoned after the translunar injection burn, leaving the Soyuz and logistics module to complete the six-day round-trip mission. Back at Earth, the Soyuz return module separates from the rest of the spacecraft, as normal, and performs a double-dip reentry to handle the higher velocity of returning from the Moon.