cant afford to buy a external flash and need diffusing solution tonight.(help)

at the expense of being a somewhat noob to photography (mainly use my a57 for video) i just want to know if anyone has any experience with the pop up flash using homemade diffusing solotiions. If you have done this before please give your input worked well for you. Im taking pictures at a bday party tonight and dont want the pictures to be blown out my the flash. I know the pop up flash isnt ideal, but its all I can work with right now.

Also. If i have a the sony a57+16-50mm lens, should I be using pre-flash ttl or ADI for normal low light shooting with the pop up flash?

Thank You.