Here is a guide on how to get bloody hands and weapons in Black Mesa.
Bloody Effects
Back in the earlier years of Black Mesa, there used to be blood on your hands and weapons when you would kill someone/thing.
(NOT MY IMAGE)
(NOT MY IMAGE)

This feature was later removed due to performance issues. But there is still a way to enable it. And it’s a lot easier than expected.
How to Get Bloody Effects
To get bloody effects, open up the developer console and write “cl_mdldetailfx_enable 1” (without the quotation marks) and then simply kill something/someone.

By Аџеј