1 – I start by roughly sketching a few different shapes for the product I am doing, in this case a simple cheese grater.
2 – Once you select a design you like, put that layer at 50% opacity and start to sketch a more refined outline on a layer on top.
3 – Finished final outline
4 – Add color on layers underneath the main outline. Use one layer per color.
5 – Shading – Use the a black airbrush at 20 to 40% opacity to shade the colors. Put all the color layers in “lock transparency” mode. This way when you shade with the airbrush tool it won’t bleed outside the colored shape.
6 – Add a metallic reflection to the blade part. I also added white highlights where light might catch an edge.
7 – Draw one of the cheese grater tooth using the same steps as above.
8 – Duplicate the teeth according to the design you want. I added a white reflection layer at 40% opacity. The relfection line is bigger at the top of the product since the light comes from the top.
9 – You can add textures on top of your drawing to give it more depth. It is subtle in this case but there is a slight brushed texture on the blade and on the plastic. I used textures I found on google and put these layers on the “multiply” blend mode. I also change to opacity to 20%. I also put the outline in “lock transparency” so I could change the color of the outline to match the red and grey part using the airbrush.
10 – I added a simple logo with a simple drop shadow and white highlights on the top edges that might catch light. You can see better in this picture the texture I was talking about in step 9.
11 – I added a grey background and used the airbrush to make it lighter at the center
12 – Once your final design is done you can easily do color variations using the Hue and Saturation tool.