Here's a quick way to use Vertex Paint to create a texture map,
and get some of the basic's in on using Vertex paint.

For this demo, I'm assuming people are familiar with;
Edit Poly, Sub-Object selections, selecting faces, assigning Material ID's,
and basic use of the Material Editor.

I used this 'Deagle' mesh

It's a unimesh, low poly, with a simple Edit Poly geometry.

First step , in the Edit Poly Modifier, lower down on the dia. box:

I selected my Material ID's and gave them a Vertex Color.
Above, you can see how the color red has been assigned to the
'Edit Vertex Colors', which has the Material ID 4.

Note: Material ID's have already been assigned to parts of this mesh:

3= trigger blue
4= hammer red
5= left pad green
6= right pad green
7= top yellow
Etc.

When I select faces of a unimesh- that make-up a 'piece' of,
or a 'part' of that mesh ( Element ), I will assign a Material ID, and Vertex Color.
( This can be VERY helpful to do- for many reasons when working in Max.)

In the above example for creating selections, & assigning Material ID's / Vertex Color,
I have selected by Element- when possible, this is faster than selecting by faces.
-a good time saver, especially for more complex meshes.

Once you have all of your Material ID's & Vertex Color's assigned,

Second step , in the Material Editor;

I put a Standard material on my mesh, and in the Diffuse box, select Vertex Color.

Now the Vertex Colors will render.

To see the Vertex Colors on your mesh in Max,
right click your mesh & select it's Properties;

select the Vertex Channel Display, and now the view port will show the Vertex Color;

Third step , now I use the UVW Unwrap Modifier;
I'll select the Material ID's that make-up the Elements of the mesh-
by showing just those ID's - see the red circle in the below picture.
Then I planar map those ID's, and 'pack' them back together. As below;

There is a LOT more you can do in the UVW Unwrap Modifier- but currently,
I'm focusing on keeping the Basic's of this process quick, and straight forward.
The red arrow in the above picture- display's the background map for the Edit UVW box.

Fourth step , Now I'll use 'Render to Texture.'
I turn the Automatic Unwrap off ( red circle in dia. below ).
I'll make sure I've got my Channels correct* ( blue circle, yellow circle ).
The green arrow below is pointing out 'layers' of Vertex Paint Modifiers in the stack,
that can be turned on and off quickly to create additional Texture maps- and, the
Vertex Paint Modifier has it's own Channel options-
( see dia. 'Vertex Paint Modifier Channel Options' below )

I use the Purple circle to point out how I like to select a large size for Texture files,
many times I will shrink that size down in PhotoShop- but I like to have the larger file to start from.

*Be sure to check your Material Editor Vertex Paint Channel too;

Vertex Paint Modifier Channel Options;

Since I'm getting into a lot of Channel info, this is a good time to mention the
Channel Info Utility, which - in Max 6, is now designed to work with Vertex Paint.

Go to your Utilities Panel, and click the 'More' button, the Utilities Window will open,
select 'Channel Info', and click the 'OK' button ( red circle's below ).

Your Utility Panel will now show this:

Click the large Channel Info button, and this window will open;

To sum up*:

*this is a direct quote from the Max 6 User Reference on the Vertex Paint Modifier- which I strongly recommend everyone check out :)

What all of that means to me - The Channel Info Box is like looking at the Layers Menu in PhotoShop. And, when you add
additional Map Channels ( 99 +3), it becomes VERY helpful for keeping track of all of the different layers.
You can combine this with your Vertex Paint Modifiers in the mesh's stack -
(turning those on and off, using blending modes, opacity settings, etc.) & get even more results.
What I do with all of this info - Experiment with it; try rendering's with lots of different channel settings. You have the
Material Map Vertex Paint Channels, the Vertex Paint Modifier Channels, The Unwrap UVW modifier Channels, The blending modes,
and don't forget when rendering -the Render to Texture Channels.
It's a good bit of info to look at, but once you try three or four renderings, with different Channel settings, it makes sense quickly. For more on this, follow the 'Continue' link at the very bottom of this page.

O.K., getting back to my Render to Texture-

I'm now ready to click the Render button in the Render to Texture.
I will create just the image file- turning off, skipping, all of the very cool shell options
possible at the bottom of the Render to Texture dia. box, keeping things simple.

This will create your Vertex Color 'Template' for the mesh's Material Map:

Fifth step, Now I'll cheat and go do a 'Google' image search for this mesh-
here's what I found;

It looked good to me, so > PhotoShop, cut and line up the parts to fit the Vertex Template;

I can now use this new map ( 'Deaglemap.tga' ) in the Diffuse Channel box of
my mesh's Material;

and get the final render.

This render is done with no lights in the scene, default scanline render.
I did cheat a little more- by adding the additional texture to the grip.

With those basic's covered, I'll now continue with more on the Vertex Paint Modifier. Continue