This article will use 3DS Max, so if you don't use that you'll have to wait until we get a blender equivalent up and running.
You will require the following plugins :
Export your detail model twice, once as modelname.smd, and once as modelname_detail.smd
Export your phys model to modelname_phys.smd
Don't change any options on the exporter plugin pop-up menu, just leave everything like it is and it should work fine.