Each fairy has its own star-sparkle animation, and if you leave the area before the animation's done, when you re-enter you can activate the point again. So you can game the system until you get which fairy you want. Just spawn an item fairy (two stars clockwise, two stars counterclockwise) and head to an area that has lots of breakable containers. You can make hundreds of coins in some areas, and quite early in the game as well. Once you get the bracelet it goes even faster.

As for boss fights, just practice a lot, use the pistol, and use Cheat Engine if necessary. I'd recommend against using an infinite trainer, though, just use the normal search to give yourself more health/ammo as needed.