Try DADGAD tuning (Low to High). It works for me with simple fingering. After seeing Dougie in concert this year I'm fairly certain he plays very little in standard tuning.
After tuning in DADGAD use the following fingers to play the chords:
D= fret the 3rd string (G) on the second fret - I use my middle finger
C= fret the 5th string (A) on the third fret - I use my ring finger
Em= fret the 5th string (A) on the first fret - I use my first finger
This sounds good both fingerpicked or strummed.

DADGAD can be tricky but with some experimenting you can find a lot of nice embellishments. Give it a try. Oh, I capo on the 4th fret but that's only to get it into a key I can sing it in. Second fret sounds right to me.