Apologies if it's wrong to resurrect this thread, but I just figured I'd toss my 2 cents in here since I recently golded this event myself and others might still be struggling with it.
The absolutely best thing I did for myself was to play the same car on the same track, but in practice mode. Bought the 8C and without fiddling anything with the setup just took it straight from the dealership and out on the track.
Seeing as you'll be driving rolling laps the checkpoint times and lap times won't be comparable to that of the Grand Tour event of course, but it is still good training. The biggest advantage for me was that when doing it this way you actually get to chase a ghost. Meaning you can try many different approaches to each turn, and get the visual feedback of exactly how much the very tiny differences can make. In addition, you get to drive continuously without being interrupted in between each lap (or even halfway through it if you hit an edge too hard).
I spent 3 small sessions of about 20 minutes each doing that, with a little break in between each sitting. After that I went back to the event. In a matter of minutes I had shaved of aprox 0.9 seconds of my previous best lap time, which was sufficient to gold it. In other words, well worth the hour of practice imho.