There is a very cheap way to get the 100-coins Shine in Pinna Park, which involves going to Episode 2. On the beach during this episode, you will have to dodge the cannon at the opposite end of the beach shooting Bullet Bills at you. The catch is that these Bullet Bills are you cash cow, as spraying them with water will make them explode, leaving behind some coins. The normal Bullets yield two coins, as do the purple ones. It’s the golden Bullet Bills that are awesome, though, as shooting them with water will yield eight coins. Make sure you pick up the coins as soon as they appear, though, as they disappear rather quickly. Remember to not get too close to the cannon, as it will switch to walking bombs that don’t yield coins.
An alternate method in obtaining the 100-coin Shine involves visiting Episode 5. Once again, you will be staying on the beach, but doing something a little different than blowing up Bullet Bills, which are not present in this episode. There are enemies on the beach called Swipin’ Stus, all of which will yield five coins for defeating each one. There’s ten of these on the beach, so that’s 50 coins right there. The other 50 coins will come from spraying water on the beach, as coins will pop up randomly.