That's it Geep, you got it.

Here is an example. I used a 3DS prop Enterprise 1701B model by Eric Peterson. I don't remember where I got this but it's an old file. Please Ignore the holes in the mesh this is just an example.

The top ship is the imported 3DS prop with 75 different materials the material names contain spaces. Poser had no problem with it.

The middle ship is the same prop exported from Poser as an OBJ and then re-imported. It now has only one material. As you see it lost all of its different colors.

The bottom ship is the result of using the work around on the same OBJ and MTL files used for the middle ship. It now has 75 materials again and looks identical to the original 3DS prop.