One size fits all (scaling issue)

Hi!
So I’m an amateur and maybe threw myself into a project without sufficient planning… but I’m trying to fix this now!
I began modeling and rigging characters and environments for a webcomic, fortunately I saw the problem before being too far in, but here: I didn’t think of modeling everything to the same scale, and now importing objects into a scene is going to mean scaling them to fit together.
I thought it would be no big deal at first, but actually, hair particle systems and procedural textures don’t scale along, shrinking a character gives him hirsute hair and a leprous complexion.
I’m suspecting I’ll have to adjust hair length and texture sizes by hand, but just in case, is there a way to resize it all in one go?