Super short tutorial : D
1st of all collect some reference, then create one circle using elliptical marque tool and stroke option. Multiply it few times created ring and each time change it vertical position size. Once that is done really important is to select all layers with created rings and align their horizontal centers, to receive perfect symmetry : )
Next step is to use brush tool or if you want be more precised pen tool and create line on one side of pot. Almost like wielding circles. Once you are happy with created line, duplicate it and flip copied line horizontally and place on second side of pot.
On one layer fill out visible inside part of pot, on second whole pot, on third it’s rim and if you want on third layer its base. When you done that, select the layer you want paint first use select pixels option on layer and have fun with painting and decorating it without worrying that you overprint other other elements. You can also use masks to get same effect.
Hope that this short tutorial will help you with creation of your own digital pots! : ) Have fun!