If you are doing a raid already found two holes with coins, there is (of course) a 50% chance to find the right one among the remaining two holes. Unless you use the two-finger trick.
In this case you have to tap both holes at the same time with two fingers and press it for about one second. Then lift both fingers (again simultaneously!) away from the phone display. If you do this accurately, the game will automatically select the hole under which the coins are hidden. Remember: This is one of the most difficult tricks – but it’s worth the practice!