I loaded a new video today to detail how to populate a level with Forest and optimize/export into Source with Wall Worm in 3ds Max.
https://www.youtube.com/watch?v=Pf3OMG4BBrI
Also, there is a new revision to the free e-book Hammered to the Max that adds a chapter on using Forest and various new and updated chapters on using Max as your level editor for Source.