Sup, /tg/.

How would you go about giving a campaign that sort of Hellboy feel?
The setting is ostensibly modern day, everything is normal and average, except that just below the surface (sometimes literally) there's all this shit concealed by glamour that was thought to be nothing more than faerie tales. Ogres, trolls, vampires, demons, all might just be living under the surface, below the streets of the world.

A sort of Fantasy Kitchen Sink sort of thing.
Any suggestions on how to make that work?

Urban fantasy! That's what it's called. How do I make that work? Without downloading all the WoD books.