Hi!
Nearly a year ago Aggro84 asked me to share my shield weathering recipe. I promised to do so and here it is. I is not "my" method of painting shields, Tom Weiss himself told me how to paint the scratches etc.
I took a Perry Miniatures Pavise and went with a rather simple geometric design.

The method works best with yellow or ocre, so I painted the pavise with Desert Yellow (Vallejo Modell Colour). I blended in some Ivory at the top and some light Brown at the bottom so simulate a zenital higlight. The pointed bar was outlined with black and filled with Hull red (VMC). Then I added more and more Flat Red (VMC) to the Hull Red and made a last highligth with pure, diluted Flat Red.

Now I mixed Burnt Umber with Black and painted some scratches caused by sword or axe strokes, which I placed mainly on the upper part of the pavise. I also painted dots to simulate spearthrusts and some irregular, larger Areas where paint chipped of.

With diluted Ivory I now painted Highlights just below the scratches and dots. I your shield is blue or green or any darker colour just mix some amount of the base colour to the Ivory.

My favourite step is to add "mud" to the shield, mostly at the bottom but I always make some mud spots here and there on the whole shield. I took an old brush and stippled dark Brown and Mid Brown on the pavise. Do not load your brush with too much paint please. Now that is all you Need to do.
I hope some of you find this tutorial helpful.
Cheers
Jan