Based on the general advice about daffodils (that you need to leave the leaves on until they turn yellow so that they get their nourishment from the sun) I do the same with day lilies and irises. I do cut off the brown flower stems. Did that to many of them today.

You can cut back daylilies whenever you wish and they will grow new leaves (unlike daffodils). You can shear them to an inch or two or leave more if there is already new growth at the bottom of the plant. However, they need to stay moist in order to regrow and some compost would help it to generate that fresh growth.

The same goes for irises, though they look rather unsightly after being trimmed and the only reason to do so is if the leaves look unsightly already due to disease or leaf death. DiSabato-Aust (pruning guru) recommends cutting them down completely after a killing frost but leaving them be until then.

Unlike daylilies, bearded iries do not tend to produce much regrowth, and if they do, it is very slow to happen. Hence, the different recommendations for each.