There is a way to speed this up a bit.
For any event that has 3 races to complete, Win 2 then DNF or Crash (you need to have terminal damage enabled for this) the car in the last one then retire. This method still wins Gold for the event for you and can save a bit of time by not having to complete all of the races.
For events with 4 races it is even better as you can DNF or Crash in 2 races.
*for DNF you have to cut few corners by going off the track.