IncludeModel Trick
Also see: Working with $IncludeModel (A Steam guide with video by Funreal.)
Decompiling with Crowbar does not get correct animation data for delta animations, so this trick is a workaround for that.
The animations are stored in the MDL file you decompiled (which I'm calling the original MDL), either from an addon or from the game itself. The trick makes it so your compiled model will use the animations from the original MDL. You copy the original MDL to a different name so your own compiled MDL will not just be referring to itself.
Copy the original MDL file.
Change the name of the copied MDL file by changing the last character. For example, if the original MDL file name is "v_coolgun", change the copy to "v_coolgu2".
Open the MDL file in Notepad++.
Change to overwrite mode (OVR), so the change you are about to make does not affect file length. Do this by pressing the Insert key to change between INS and OVR shown near bottom right corner of Notepad++.
Click on the last character of the MDL file name near the start of the file on the first line. A blinking underscore should be under the character.
Press the key of the new character.
Save the edited file.
In the QC file, delete all $sequence and $animation lines.
Insert a new line, $includemodel "<copied MDL file name>", for example: $includemodel "v_coolgu2.mdl"
NOTE: If the $modelname line of the QC file has any folder path before the MDL file name, then you need that same folder path for the $includemodel line. For example, if your QC has $modelname "v_models\v_coolgun.mdl", then the $includemodel line should be this: $includemodel "v_models\v_coolgu2.mdl"
Compile the model based on the edited QC file.
Include the copied MDL file with your other compiled model files in your addon.