I had the same problem like you :)
When installing xrdp, xfce and changing the xrdp.ini (as shown in your own answer), I was able to rejoin to a remote session. Still, I was unable to share the desktop, in other words to rejoin the local session.
The vino stuff does not work for me, I got the message "connecting to 127.0.0.1:5900 error - problem connecting". From my point of view, this is because of a missing vncserver as iain-samuel-mclean-elder points out in a comment.
Long story short, I managed it to work properly with x11vnc. When the computer starts up, a service is calling x11vnc.
Maybe the following will help others, so, they do not have to search around the internet the whole day, like I did.
The instructions you need to follow are only from the two links below.
--> I just changed the /etc/xrdp/xrdp.ini file to my own needs:
The nice thing on this set up is, if you connect from Windows with the standard rdp, you can reboot the computer remotely and connect remotely again you end up on the normal log on screen of the computer as you would sit in front of it. Choose "Local Session" on the xrdp menu after connecting with rdp. The password is the vncserver passwd, which you chose, when you followed the c-nergy-link above.
If you just want to open another session, you can go for the "remote session".
Hope this helps ...