Here's the shield we are going to paint

Deciding what you want to paint on the shield is the most important step. To much detail and you have to be Michelangelo. Here I picked a Unicorn from my Heraldry book.

Next we use a very diluted white paint (Coverage is not important but you want skim milk or less) to sketch out the shield design. As you can see this is pretty rough. Where not worried to much about being precise we can clean up later.

We fill in the figure with our diluted paint. Again coverage is not important.

We just add more white paint keeping our paint very thin. Add layers instead of using thick paint. (If you screw up the paint will easily be covered up because it will be very thin)

k...we are going to start adding detail. We use a very thinned version of our Base Shield Color. Note this is actually a slightly darker version of the shield color, but because it has been heavily diluted and going over white, it Looks light blue.

We just add more layers of our blue. Note it's getting darker, and we are using the same diluted blue paint.

Clean up stage. We go back to our white, fill in detail.