I'm trying to create custom clothing meshes for the sims 3, I've done it before with the sims 2, is it done the same way with rigging it in milkshape? are there any tutorials on how to do this?

I never had TS2, and never made anything for it, so I have no starting point for how much you know. I use Blender for meshing. A combination of Smug Tomato's tools for Blender, and Meshing Tool Kit when exxporting as object.

First thing is to use either S3OC or TSRW to extract a mesh to work with. There are several meshing tutorials here on MTS, and 100's on youtube and elsewhere on using Blender.

Whatever you do, it must match to the EA rig as far as I know. Smug's tool will import a rig.