For me, it worked only after emerging the utility packages described in the pulseaudio.org site :
emerge pavucontrol pavumeter paman padevchooser paprefs
Then, starting the alsasound daemon (added to boot runlevel for next reboot).
Then, simply typing "pulseaudio -D" (-D is for daemonize after startup), as user, not as root.
Now, my audacious is playing using the pulseaudio daemon server, but still no sound in swfdec (I was hoping this could give me sound in youtube). I'll try to restart firefox just after this post and see if there was missing just a firefox restart...
Hope this helps