Adding a custom model to the toolset tutorial
This tutorial describes how to add a custom model to your Toolset. It is assumed that the reader is familiar with the Toolset.
Download tazpn's Command Line Tools 
or alternatively use
Allstar's GUI interface for Tazpn's Command Line Tools 
Convert your model to DA:O compatible files
It is assumed that the model is finished and textured.
Export your model as a *.fbx file.
Use tapzn`s Tool to convert the *.fbx file to a *.mmh.xml file (fbxcmd convert name.fbx name.mmh.xml). You will get 3 files out of this:
Since the *.mao file is not well named in some cases, you have to manually rename it. If you do this, don't forget to change the reference in the *.mmh.xml file!
Just drag and drop your *.mmh.xml on the "\Dragon Age\tools\ResourceBuild\Processors\MMH\GraphicsProcessorMMH.exe"
Copy the *.msh.xml file to "\Dragon Age\tools\ResourceBuild\Processors\MSH" Then do "GraphicsProcessorMSH -platform pc mmdtogff (filename).msh.xml" using your Shell / cmd
Adding it to your Toolset
Copy all the files (*.msh, *.mmh, *.phy, *.dds, *.mao) to "\Dragon Age\packages\core\override\". Optionally you can pack it into an *.erf file. The builder to player packaging process can package up these files into an erf for you in the process of creating a dazip installable file.
Using it in the Toolkit
To use it in the toolkit you have to specify which item variation your item is. Edit the fitting *.gda in the 2da.erf to do so. See ItemVariations.xls.
If you did nothing wrong up till now, you should be able to use it in the Toolset by now.