Mats -- Chipped Paint, chrome dirt map

Model has UVW from Box mapping

Texporter setting

Beneath the wireframe template, start with a plain but not completely flat surface like this “generic base” file ...

Use HSL to colorize the lower layer

Duplicate and make a lighter top layer

Open up a chipped wall texture like this one ...

Adjust curve to make it black and white but not jagged ...

Make a layer mask and paste that texture into it ...

This is just the beginning ...

Make additional layers of color ...

Paint dirt with a soft large brush set to multiply ...

Make a dirt layer with a dirt texture image and a grunge mask ...

Work on cloning dirt into the seams of the model.

Work on creating streaks from wind, gravity, etc.

Finally, make another grunge mask, and use it in a BLEND map in max ...

This is the MASK:

Material 1 is the standard map in Max called Metal_Chrome.

Only ½ of the body has the corrosion material ... look closely and observe the difference ...