If you aren't the best racer out there, but don't want to let a hired driver do all of the work for you, you can do what I did ... and this should also help you get to Level 50.
Go to the GT Championship of Japan Series in the Regional Championships (must be Level 35 to enter). Enter the second race of the series, the Nissan Speedway.
Personally, I used the 2005 Toyota #36 Open Interface Tom's Supra (Class R3) because of it's stats and decent handling capabilities. However, any car you have that you are comfortable with can be used. For the difficulty settings, I chose:
Suggested Line: off (+10%)
Anti-Lock Braking: ABS off (+10%)
Traction: TCS on (0%)
Stability: STM on (-5%)
Shifting: Automatic (0%)
A.I. Difficulty: Easy (-5%)
Damage: Simulation (+10%)
Fuel/Tire Wear: Simulation (0%)
Reason I chose these settings: On this track (basically a big oval) and with this car (pretty good handling), all you need to do is floor the gas and steer (minimal steering). You should never need to use your brakes or slow down, and you should never hit the wall (once or twice at the most if you're not paying attention ... surfing TA like I was) and you should blow the competition away just past the starting line. However, the stability and traction do come in handy. I did try A.I. Diff. on medium, but I had trouble catching the lead car (for some reason, there was a world of difference between easy and medium).
With this race, and these settings, you should net a little over 41,000 CR in under 8 minutes; about 287,000+ CR per hour. Not a difficult track, easy competition, and very little effort.