Converting Black Mixes In Prepress

Does anyone have any suggestions on how to treat varying black mixes before the job is color-managed. We receive customer files where the black mix ranges anywhere from single-color to 400%. In the past, we’ve always converted them to a target mix, either in Photoshop or Illustrator. Now that we’re beginning to use color management, I’d like to streamline the process. Our device profiles do a pretty good job of bringing them all to a rich black, but there are still differences. I’d just like to know what some common practices are. Our target profile is GRACoL and most of our presses are large format ink jets.