How to Paint a Realistic, Dimensional Red Delicious Apple

In watercolor, I find that I am able to achieve the most realistic dimension by layering. First, I find the highlights and where white, I leave the paper dry. Where the highlight is slightly bluish, I wet the area and slightly beyond, wait for the shine to leave the area and paint the thinnest wash of thalo blue into that area. I dry the paper completely before proceeding to the yellow underlayers.  One of my favorite teachers, Susan Tustain Harrison (link) uses a priming method to gradually build up layers of glazed thin color even as she builds her under layers. To achieve the depth of color, in these yellows Susan would have painted 3-6 layers of thin color. Each layer would have been primed, color applied and then dried before the next layer was applied. I am too impatient so I wet the area thoroughly, watch for the shine to disappear and then apply the under layer in 1-2 layers. Here you can see the under layer is two different yellows: warm indian yellow on the left and cooler aureolin yellow on the right as you look at the painting.
Because this is a deep red apple, the under yellows need to be an intense yellow color.

After the paper is bone dry, I paint wet on dry with soft brushes to not disturb the underlayer(s) of paint. For this layer, the reds are mixtures of alizarin crimson, scarlet red, translucent orange and permanent rose. Going from the darkest red area beside the bright yellow: you can identify alizarin crimson, then scarlet and translucent orange in the area around the white patch of highlight, then thin areas of permanent rose or permanent rose plus scarlet and on the outside right area scarlet and a touch of alizarin crimson.The shadow is started by wetting the shadow area and then running a line of clear water along the bottom of the still-wet red apple and allowing the paint to run into the shadow area.