What's the most quick and efficient way to earn credits after you beat the main story? (spoilers?)

You can’t redo the final race anymore, so is the best way just to as you did before and go around doing different championships and challenging high-value racers? Or has someone found a better way of earning mass amounts of credits?

I think you nailed it. Keep playing the game, racing head-too-head and play multiplayer. Keep getting those wheel spins.

Except that you can re-race the finale. You need to unlock it again by winning 15 more regular Championships.

been racing online (360) and with the settings i got, i pulled in about 850,000 in 2 days. but of course its depends on your assists as well as your finishing positions.