Shell mods
Notches
Subtly changing the shape of the gate to add notches in specific places makes hitting certain analog values easier.
Retrobright
Use hydrogen peroxide to remove yellowing from clear or white shells.
Shell dyeing
Dye a shell to give it a different hue.
Shell painting
Painting a shell is the most popular way to get a fully custom shell design.
Shell tinting
Spray paint the inside of a clear shell to give it a splash of color.