Carnage is right, with the loss of both engines (AC BUS 1+2) the RAT should deploy automatically. On deploying it powers the blue hydraulic system, which drives the emergency generator by means of a hydraulic motor. This generator supplies the AC ESS BUS, and the DC ESS BUS via the ESS TR. This will result in P1 displays working and P1 comms working. As for the Hydraulics at low speeds (which you will be in the glide) only the blue Hydraulics will give pressure so you can deploy Slats only. The checklist though calls for you to move the flap lever to Flap 3 position incase of residule pressure giving a little more. Interestingly last time I was in the sim we were doing Dual Eng Failures from altitude and it was debated as to the merits of starting the APU, risk is that if you attempt a start and it doesn't start for some reason then you have severly reduced your available battery capacity. If it does start however then you regain electrics, possibly can start the Yellow Electric pump to gain full flap availability etc.