08 Scion xD, Hazard Flasher for Brake Lights?

i have a 08 Scion xD the long story short i want to add a second hazard flasher to my car on its own switch to be used to flash the park lights and brake lights. (please note brake lights and not running lights. [although i think the park lights would be tied into the rear running lights in which case i can live with it]) i have added brake lights on my car and for show purpose i would like to flash them to show they are there and lets face it flashing is cooler then just making them constant burn right? so, i go to my local auto parts store and pick up a flasher relay, what next? lol.      Parking Lights           GREEN           (+)           AT VEHICLE FUSEBOX      Brake Lights           GREEN           (+)           AT SWITCH ABOVE BRAKE PEDAL