Drakhen , i do not have a ps3key in hand , i build my own teensy 1.0 version , but i assure you that it is possible to have the DFU mode and reset on the same button. The way DFU is triggered, is by checking a line upon reset , if that line is low, it will enter DFU mode. It is very easy to build logic around both the RESET and the DFU pin bringing them to a single pushbutton switch.
Christos, if it does indeed have a button, put the dongle in your PC , press and hold the button 0.5-1 second , and release. This is the DFU mode. If its the first time you use an Atmel MCU in your pc , you will be asked for drivers. They are located in the \USB\ folder of the Flip install folder.
Once you have the drivers, inside Device manager you will have a new category, ATMEL USB DEVICES , and inside will be listed the number recognized for your chip. Use that chip # when selecting a device from Flip , then click the usb cable icon to "load" the chip. Once the chip is loaded in Flip , you select the correct .hex for that chip , and just press RUN. 3 seconds later your chip is programmed.
Insert dongle in pc , if its already flashed , you might see USB HUB , then unrecognized.
New device detected , requires the USB drivers.
Verify in Device manager