Dude, unless you have a bootloader, you must use SPI. IIRC, the bitbang pins are located on CBUS. No data from CBUS (except leds) goes to the SPI pins. Or maybe the bitbang is on RX/TX, still, those pins go to the MCU TX/RX.
You say you don't have a bootloader. So, how is this thing programmed?