I am also intrested in this topic.
I use mc (midnight commander) as my main file manager. It have one disadvantage: copying files is in the same thread/window. When I copy/move bigger files, my file manager is frozen...

I would love to have a script that calls thunar via dbus to copy/move/delete files...

On GNOME installation I use udisk and gvfs.
On my XFCE instalation I tried a little experiment to go without these with a static desktop of mine

E.g I created my own desktop files
$ ls Desktop/*.desktop
CD-ROM.desktop  Computer.desktop  Floppy.desktop  Trash.desktop  USB.desktop

For my trash I implemented a simplified function, perhaps even a buggy one,
#!/bin/sh
if [ -n "$1" ]; then
        for f in "$@"; do
        echo $f
        if [ "$(stat -c%m "$f")" = "$(stat -c%m ~/)" ]; then
          echo same file system, moving to trash
          mv "$f" ~/.trash/
          [ -e ~/Desktop/.tmp ] || \
            sed s/Icon=xfce-trash_empty/Icon=xfce-trash_full/ \
            ~/Desktop/Trash.desktop > ~/Desktop/.tmp
        else
          echo different file system, removing in place
          rm -r "$f"
        fi
        done
        [ -e ~/Desktop/.tmp ] && mv ~/Desktop/.tmp ~/Desktop/Trash.desktop
else thunar ~/.trash
fi

Instead of using mv and rm in the above shell script, I thought it would be nice to call back thunar possibly using dbus messages.

Is it possible to send a dbus message  to Thunar?
I mean if a user can send a message such as copy, delete, move file from a shell script.

E.g.

$ dbus-send dbus-send \
    --dest=org.xfce.Thunar \
     /my/file/name \
     org.xfce.FileManager.delete
....

If so, where do I find the docs on the supported interface?

Many thanks