any time I've used spices, I always boiled/steeped them and they went into primary.
adding to secondary, if you want a rum taste, soak in rum.
otherwise i'd steep em in vodka for the neutral flavor.
or steep in boiling water and add to secondary vessel and then rack the ale on top to mix.
Primary: English Mild
On tap: Pale Ale, Lancelot's Wheat, English Brown Ale, Steam Beer, HoovNuts IPA
Bottled: MOAM, Braggot, Raspberry Melomel, Merlot, Apfelwein, Pyment, Sweet mead, Cabernet
Gal in 2009: 27, Gal in 2010: 34, Gal in 2011: 13, Gal in 2012: 10