White IPA adding spices

So I brewed a white IPA 3 weeks ago. When I went to the home brewstore I forgot to pick up the spices I was "supposed" to add to the boil (lemongrass, orange peel, and sage). I went through with the brew anyway. However, I still want to add these spices. What's the best way to do it? Add it to a hop bag and dry hop with it in a secondary? How should I sanitize them? I was thinking of soaking them in vodka then dropping 'em in.

Since no one had any breath taking advice I used ideas from this link. http://hollisbrewco.blogspot.com/2011/10/making-spice-tinctures.html

Mixed .25 oz lemongrass, .25 oz orange peel, and .1 oz sage. Let it sit in ~ 3/4 cup of Vodka for about 30 minutes. I then filtered it through a coffee filter a few times and dumped the Vodka tea into the keg. I transferred the brew from the primary right on top. Very excited to give this a try in a week or so.

Sorry I didn't see this question earlier.
You found a great method to use. The beauty of this is the amount of control it gives you. Next time consider dumping "to taste". Keep adding and tasting until you get the flavor you want. This is what I do with chili peppers. Their heat can be so unpredictable.