One technique for bringing out highlights within a shadow area is to use a bleach such as potassium ferricyanide. Make your print as usual (on FB paper), and wash completely after fixing. Mix up a very dilute solution of potassium ferricyanide, and paint it onto the area of the print where you want to pop out the highlights, and rinse the area almost immediately with running water. The bleach will take away some of the silver which leads to darkness and enhance the highlights. It works better at bringing out detail in highlights and doesn't do much in the shadow areas.