Using PxrCryptomatte workflow, you can output IDs in Katana for easy selection in a compositing application. You can then use that selection as a mask to make changes selectively in post packages.
PxrCryptomatte is supplied as a Sample Filter plugin. As such the output for Cryptomatte is stored as a separate EXR file from your beauty or denoise outputs. Please note an OpenEXR output (file.exr) is required to store the values correctly.
We only render this when using a disk render to avoid overwriting files during an interactive session
The attached example file for Katana workflow.
This file contains two PxrCryptomatte nodes to output both object and material IDs.
Render your scene and look for the output EXR in the path you defined above. The example file will output two EXRs, one with Object IDs and another with Material IDs as seen below.
You can download the above scene created in Katana 2.6 v4 as cryptomatte_filters.katana