On stage 3 round 2, there is a pig on an airbike. Defeat him and collect all the gold afterwards. After gettung all the gold in the area, there is a "gambling game" nearby. Go up to it, making sure you have things to shoot at it. Use a Slow. When you hit the target at the correct time, lots of gold will appear. Collect the gold, then continue. As you go, use a Fast Forward to make things go faster. After awhile, the gambling game will be spinning again. Repeat the process with the allotted time you have remaining.