There's an interesting book called "African Guitar Styles" by Folo Graff (A.D.G. Productions 2001) which comes with a cd. I don't know whether it would directly assist the interested student of guitar with Matthews' songs, but it would widen their rhythmic toolbox a bit.

The guitar is, after all, a percussion instrument among other things, though a little more evolved than the bodhran.

Peace, Mooh.