There is no DCX Studio available. It's open to anyone that wants to build the application.
There is also a lack of tutorials or other material simply because the DLL is still in development (we're almost at an official release).
Most features are implemented, I'm mainly in the phase of correcting bugs found and implementing useful feature suggestions submitted by users.
There is one important thing to note, DCX does not work like MDX so there will be a learning curve for people used to the MDX way, but they will finally find that DCX is more natural in the way of processing information in the controls. There is no reserved line 1 like in MDX and the controls are not hosted into mIRC native controls. Also, DCX offers infinit container recursion of controls with it's rebar, panel, box, divider and tab controls. So you can build complexe UIs using all these tools.
Input and Output from controls and dialogs are done via the supplied /xdid, $xdid, /xdialog, $xdialog commands and identifiers. These are used exactly like mIRC's /did, $did, /dialog, $dialog.
Events are handled with a "callback" scheme which mens that the user can interact proactively to certain events to prevent the default action to be done. (A quick example is prevent the headers of a listview from being resized for example.)
There is a file called dcx.mrc in the DLL package which is used to test the DLL but also illustrate how each control is created and used which can act as a first tutorial contact with the help file to start using the DLL.
Once the userbase grows, we will probably see some specific tutorials emerge and hopefully a DCX Studio.