We usually peal back the two green parts that cover the blooms to expose the flower and then thump it with finger. Is there a term for the flicking action? Any ways it usually cracks them open and you can help it along by unfurling the bloom.
Make sure the stems are cut past the white part at the end of the stem.
In otherwords, the bottom of the stem should be green, not white.
An empoyer early in my career would NOT cut the stems, leave the white part there, put the iris in the cooler WITHOUT water. Reckoned she could hold them a few days longer.