This seems to work on any surface plastic,wood,metal whatever.
The secret is in surface preporation.It works even on a highly polished enamel surface.
Prepare the surface by sanding off the shiny new surface with 600 or higher sandpaper.You want to dull the surface not create scratches.Rub until all the shine is gone.Next paint the surface with a 50/50 gesso -water mix and dry with a hair dryer if you like.Dont set the hair dryer too close to the surface but just blow the warm air across it.(you can always just air dry it if you want)
Now if you want to put some color on, put it on in thin layers (at least a 50/50 mix,even more water if you are using tube colors)Dont completely cover the gesso surface with a solid new color if you want a real antique look,some of the undercoat should show through.
Now the fun part.Take some watered down burnt sienna and using an old brush and a washboard surface vigorosly scrub the paint until it foams up.Then take this foamy paint,bubbles and all and dap it onto the surface.Dry with a hair dryer and repeat as many times as necessary to get that nice rusty and corroded looks.Works great on old barrells,oil cans,engines ,cars whatever needs antiqueing.Take your time and have fun,I sure am.