Your friend's suggestion is spot on.
A shot or two of vodka in a small bottle (or mason jar) with a 1/2 teaspoon, or more of each spice-even the orange peel-let it sit for a week or two (or longer if you have time).
Filter through a coffee filter to get just the liquid, and add to the batch at bottling time.
Add a little at a time, stir gently to mix it in, then taste. Keep adding a little until you have the right hint (or punch in the mouth) of flavor. Then bottle or Keg.
That is basically how you make your own flavor extracts.
-Those that know don’t close the door on those that don’t know (The Gourds, "Education Song")...
-The brewer's yeast ferments, and forgives, all that you did...(The Gourds, "Right in the Head")...