This should work as well as Plasticote. Both are quality products, with the Duplicolor sold through auto parts stores.
I would recommend that before you spray on raw styrene you spray a test coat on some scrap or sprue to see how it behaves. Resin is generally not affected by the solvents in spray paints and will not craze. Styrene will craze with some of the hot solvents in lacquers. You may need to spray lighter coats from a greater distance until you have a base built up.
Red primer colors vary from manufacturer to manufacaturer. Their use is a matter of personal preference. I have a collection of samples of various primer reds and some model paints used for hulls. I love the American Traditions from Lowes Red Primer - a rich orange/red/brown. I dislike the American Painter brand from Home Depot - too brown. Personal choice
http://www.duplicolor.com/products/primer.html
From the color sample linked from this page it looks like it would be an excellent choice.