Setting up a Mod Normally:
If anyone wants to use custom stuff with their mods, create a folder called custom inside Half-life 2/hl2 and/or inside the ep2 and episodic folder. Never simply put models/materials/sounds inside the custom folder, you must make your own folder inside there first!
For example: ep2/custom/my_custom_folder
Then just open up a sourcemod's gameinfo.txt and add this:
Make sure it goes before any other game+mod or game_lv listed there, in order to make sure that the custom stuff loads first, otherwise standard hl2, ep1 and ep2 valve stuff will end up being used.
It will load all the custom content in all your custom folders. If you don't wish for all of it to be used then you can simply replace the asterix with the actual name of the folder you want used inside the custom folders.
For example: game+mod ep2/custom/freddymercurys_custom_stuff
Please note that this functions in the same way the hl1 system worked. So that if a mod has its own custom content, than that will be used instead of your custom version. So if a mod has its own pistol model, if you want your custom pistol to be loaded you'll have to manually delete the files in the mods folder that you don't like.
Eg Personally I delete skill.cfg in a mods cfg folder so that I can keep my difficulty modification working.