assign a color in moi to the parts that you want to be the same material in blender. (IE bolts are blue, Plastic is orange, wood is green, etc) they come into blender all with those separate materials. all you have to do is modify one of the bolts blue materiel and all the other blue bolts will be modified as they all have the same material. you can apply multiple colors (materials) to one object in moi and it will be imported into blender.