So I am doing this on the last day, with less than 24 hours left. For those of you in a quick rush, this is for you.
We were lagging out and our games were sending us to the home screen and such, and we were looking for a fast way to do this challenge.
What we found was that, when you start an in game party, all you have to do is
1. Drive to the "start" of an event. So that it says like event 1/4 or whatever.
2. As soon as it says, "Get," "Ready," "Go!", hit start and choose quit (all of you need to do this).
3. Do step 1.
4. Rinse and repeat until you start event #4.
5. Complete Event #4 and you will gain progress towards your challenge once you are getting the championship exp, that is when your challenge will go up by 10%.
Saves time because you do not have to complete Event #1, 2, and 3. And if your partner gets to a finish line first, at any time, you do not finish at all, that is fine too. It still counts. You do not need to pass a finish line. Just have to be in there from the beginning to the end.
Hope this helps guys, less than 24 hours left until this goes away.
Here are 2 videos from the Twitch stream that I did, they show you that you do not need to complete the race, and when to quit, and that all you need to do is start the event.