Not sure why anyone would want to paint a car gold, so I can't answer part 1
As for part 2, I recommend high downforce, plenty of camber (-2 to -3), steering sensitivity on 2 or 3 and run gears as follows:
Fuji: 255
Indy: 255
Cote d':196
Ring: 211
Monza 255
Not sure about Suzuka tho, I did it separate from the championship and didn't note the gears. In the championship race it was raining and since I was more than 100 points ahead, I started, then abandoned the race. Note, if you do this, you must at least start the last race, if you opt out from the 'between race' menu, you'll simply exit the whole tourney and get nothing.
