I could never complete the final cup (there are only three, I'm guessing it's the same one you couldn't beat), or actually even win a single game in it. I ended up just downloading a save file from GameFAQs so I could have all of the characters, stadiums, and options.
I don't think you're the type to use the exploits, at least not in a friend match. It's kind of necessary if you're playing random matches and the other player is using them, because the only real way to counter is to use them yourself and hope you end up with more points. Of course, I don't really know HOW to use the exploits so there's no way I could win against somebody who does.
These days there are three types of players who play the random matches:
1. Those who use the exploits.
2. Those who score a goal and camp on the opposite side.
3. Those who spam the same cheap trick.
I don't know if I've ever come across a random player who actually scored by kicking the ball into the goal. It isn't even football anymore. It's asinineball.