Size six means Pay! Shoe modeling is a good job for a petite model.
Footwear Plus is a trade magazine that models that want to shoe model should read, also pay attention to shoe ad campaigns and tradeshows in NYC, VEGAS and nationwide that need shoe models. Even without an agent you can simply email a brand and ask if they need a shoe model. Usually it can get you a great gig that will last a few days shoe modeling at the shoe shows that take place 4-5 times a year. To submit yourself you do need to have a nice photo of your feet, something simple, to the point, basic, and you need a shot of your whole body, and also one just of your foot as well.
If the shoe company is for sneakers, don't send a photo of yourself in high heels, market yourself for the products you want to model for.