Pulseaudio/X permission other user/SSH

My user user1 is running a graphical X session with pulse configured per-user. I need to run a graphical program that uses audio with user2. - If I do su user2; program program doesn't start and I get no audio neither video - If I do gksu -u user2 program the video is working, but I get no audio. Why there are these problems? What is the right way to start a pulse application that outputs sound on the pulse of my user? What the right way to start an X/audio application from another session(for example an SSH shell)?