I do something similar, but use thin dark steel pans that are for 4-square pizzas. I know you aren't trying to make Detroit style pizzas though. I have tried vegetable oil, corn oil, MFB (something like Crisco) and those all seem to work in making the bottom crusts crispy and the bottom crusts do brown.
Maybe if you can post a photo of what style of pizza you are making other members might be able to help you. Also you might describe what style of pizza you are making if you can't post a photo.