It should be common knowledge by now:

1) The three-hour-instant-service starts right at the moment when you start the game. Not when you start the first race. So if you want to use the instant service, make sure you've got 3 hrs time to race right away. The countdown will start right  after opening RR3.

2) Even if you miss the instant service, you still can get additional 5 GC on each Friday. I haven't found a pattern, but you'll get the 5 GC throughout all Friday. Just click on Erik's button, whenever he shows up on the start-up screen, maybe you'll need a restart of the game, too. Any 4 or 5 or whatever races, any 15 or 30 or whatever minutes, any CS in between? I don't know.