As soon as the pokemon breaks out of the great ball press the home button and close pokemon shuffle and re-open it. The 2500 coins it subtracted won't have been subtracted, but it won't register you having beat the pokemon (which doesn't matter if you just want to catch it...)
Pretty sure he's asking about the home button trick to chain swaps. I would like to know the answer myse!f, actually.
My current score is 16891 with a rank of 1766/117904. Well my score is higher than that time with Lucario so... I think I'm safe for now.