When I've driven with the driving line on the 'Ring previously, it's been overly conservative*. That's fine for getting you around the track, but I think it would leave you several seconds short of a winning time in this event. It might be useful for getting a baseline for your braking points and turn-ins so you can start figuring out where you need to be more aggressive, and by how much. For that purpose, though, you'd probably want to just practice-lap the track or run one of the endurance races so you can run a bunch of laps back-to-back, instead of having to restart the race after every lap. Practice-lapping would give you the advantage of feedback at the splits to see when you're finding faster lines, though with the negative that red-timed runs wouldn't stick (whereas the endurance races will keep every lap but won't give you feedback on your split times, you would have to remember the quick splits on your own, and tire wear would limit you to only one or two flying laps in a stint).
(*Caveat: I haven't driven with the driving line on with the Gallardo, so it's possible it's more accurate.)