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.

...

Example Workflow:

1. Create a PxrCryptomatte node. Specify the file name and path. The example file uses a script to write to your Temp directory.
2. Layer: Select the layer type, Name (object) or Material.
3. Connect these to a ShadingNodeArrayConnector
4. Create a PrmanShadingNode and select PxrSampleFilterCombiner. Connect the ShadingNodeArrayConnector.out to the input of this shading node.
5. Create a NetworkMaterial node , right-click and "Add terminal", select "samplefilter" in the Prman dropdown.
6. Connect the prmanSamplefilter.out to the NetworkMaterial.
7. Merge the above network (easy to reuse) into the trunk.
8. Create a MaterialAssign node and assign the Cryptomatte NetworkMaterial to /root

...