You need to learn how to airbrush — using a paint nozzle that mixes pigment with air to make sprays of varying density and color intensity. Then you can lay down softly graded tonal values of a single color. Next, you need to study metallic highlights on metals, satins, glass, etc., until you understand how to place the lighter versus the darker colors to create shiny effects. Google 'airbrush' or get a library book on the technique to learn how.
It may depend on what medium you use, but a glossy art paper with a hard surface will give a shiny look. Bristol board has a hard surface. Water color papers generally have a matte surface. Of course you could always laminate your work with a shiny plastic.