optimisation

Hello, a few days ago deepedia asked why there were huge texture files that most people would simply resize in order to use them. This, I think is called 'optimisation'. I rework some .obj files because I can't find new items for the V4 figure. Quite a lot fall into the general size of 2MB, some less. I started to find some above 6MB, not just 'cloth' but hair. Hair also seems to make a render engine really 'chug'.
My question is:
Is there a way of reducing the resolution of a quadrangled .obj file? I have seen some applications but most seem to be for triangulated objects. I can't find a reliable review on any of them. I was looking for a stand alone prog. I tried Blender but I'm unable invest in a new computer at the moment. I use Wings3D, this is probably the only thing it can't do easily.