Create a shortcut in your "SendTo" folder that points to L4D2's VPK tool. This will allow you to "send" your addon folder "to" the VPK tool that will create the addon vpk file. It also allows you to "send" a vpk file "to" the VPK tool that will extract all folders and files from the vpk file.
Go to "C:\Program Files (x86)\Steam\steamapps\common\left 4 dead 2\bin" folder.
Right-click on vpk.exe.
Select "Create shortcut".
Right-click the newly created "vpk.exe - Shortcut" file.
Select "Rename".
Change the name to "L4D2 VPK".
[TODO: Describe setting up of toolbar shortcuts for the other tools.]