I change the FD and gearbox in my 08 every two years or 10,000km, whichever comes first. BMW recommended SAF XO for my model, the product can be purchased from the local BMW dealer or Supercheap Auto. Only takes one litre for both the gearbox and FD. I always leave 200 mL for the FD. I use the filler plug but true its also good to clean the induction speed sensor so why not put the oil in there.
I just use a 100 mL syring with a 6mm x 4mm clear extension tube for the FD. They say not to touch this oil with your fingers, so I use the one syring and keep it in a zip lock bag for next time. It gets rinsed with a couple of squirts first into the gearbox then used for 200mL into the FD.