Sometimes it is better to work with another choice than "planar map", because some vertexes get very worth with special choices. but that delivers in every case. Maybe it is good to detach some parts, to unwrap them and you again attach it to one model after it. After unwrap, set an extra modifier "edit mesh" on one part and then attach the other parts.
Very often it is easier to do so. But it is different in every case. So you have to try out. There is a "render to texture" featur under "render" in 3ds max 5 and 6. this is a "automatic" unwrapper. In 3ds max 6 you can work with the unwrapper seperate to texture render in 5 you must do both as I remember.
Than you get an uvw for the model. Save the uvw in an extern file an reload(in 5) or simply delete the automatic uvw modifier(in 6). Then do an "uvw unwrap" modifier on the model(selecteing all vertexes) and load the saved uvw.
This "Automatic Unwrap" is not very good(you have to move, attach and sclae also a little bit), but sometimes it helps to keep time for more important stuff). But as I said before: try out and find the best solution.
