Hi Sid,
that's a really good question. Sorry if this is late news, as the OP was ages ago. I'm only a rough, noob HBer but I'll happily share my own experiences, mostly from trial and error with k & k.
I too, wondered about that very same thing when I had a Muntons' Irish stout underway, so I decided when I was about to bottle to:
1) Roughly crush some star anise and bruise some juniper berries in the mortar and pestle, just crack it all enough to fit through the neck of the bottle and get the juniper berries opened up a bit
2) Sanitise that in a sugar- sweetened (don't ask why, see below... a few tablespoons) 1/2 litre of water on the stove gently simmering for 15 minutes
3) Through a funnel, distribute this evenly into each of the target tallies (I did just 10 out of 30- odd in the batch) along with priming sugar (I used lollies because I've got two left hands...)
4) Bottle as normal
From the second batch, I dropped the extra sugar- I was very green at the time and yes, it was a big mistake, just part of the learning experience. It is entirely unnecessary, unless you happen to like a third of each bottle disappearing frothily down the sink when you open one up. [Slaps forehead- should know better by now] Silly me... The reason I used sugar with the spice originally is that I though it might need a 'carrier' or something. I see now that I was probably mistaken...
But I tell you, for me anyway, it is just to die for! In the primary I just used the Muntons can, a bag of Brewcraft #74 sugars, a bit of extra dex, no other hops or anything, just the spicy adjuncts, that's with me still being in HB kindergarten (but a slightly rebellious problem child!),. The juniper berries aren't that up front, they're fairly well lost in there in fact, but that anise is just marvy. A really hearty and totally different stout, but I really dig it, even in summer (as I just so happen to be doing right now!).
My second attempt (sans extra sugar) is much the same (less waste though- surprise, surprise...), but I wonder if the adjuncts would be better going in the primary ferment (or the boil, if I ever graduate), the HB wizards out there will probably have an opinion about all that. The amount of star anise wasn't outrageous, probably about half to one star per bottle or thereabouts, maybe three or four juniper berries for each bottle, but I'll probably drop the berries for the next one.
There is always room for improvement, and I'd welcome any suggestions of course, particularly WRT hops or when to add the star anise with k&k methodology. That's an area I'm not at all familiar with and would appreciate directions. I like the English Bitters and brown ales, plus dark, rich stouts as well of course, if that's any guide.
Did you take the plunge with yours Sid? If so, how did it work out? Obviously you've done the boil biz and have the benefit of all that and a few more opportunities for adding some anise there, I'd imagine there are a few different ways of doing it and I see a few from googling it.
Anyway, cheers for now,
RdeVjun.