Here's the method I used a few months ago for my jalapeno-infused "Hot Blonde" Ale. I'm sure you can use it equally well with any variety of fresh chiles. If you want good pepper flavor and only a little heat, you might consider poblanos- I think they might work pretty well in a stout. Or you could mix some "flavor" peppers and some "heat" peppers (poblanos and a little habanero, maybe?).
I cut my peppers in half lengthwise and then into roughly 3/4" slices to expose plenty of surface area, then soaked them in vodka. I left the seeds and membranes intact, as this is where a lot of the heat lives. I used "regular" 80-proof vodka, but presumably a higher-proof would be a more effective solvent if you wanted to spend the $$$- I just used what I had in the house and it worked well enough, maybe just took longer to get the full extraction than it would with a higher proof. I did 2 or 3 jalapenos in about a pint of vodka and let them soak for about 10 days, then poured it through a coffee filter to strain out the peppers and seeds, leaving just the infused vodka.
As far as getting it into the beer, I added the infusion at bottling time- you've already extracted the flavor with the vodka, so you really aren't gaining anything by adding it earlier. I filled a glass with 12 oz of beer (one bottle's worth) and added the infusion with an eyedropper a little at a time, tasting between additions to see how much would give me the flavor and heat I was looking for. I wound up using about 20mL/bottle, so you can add it by the dropperful- no need to go drop-by-drop unless you're using some really insanely hot peppers. This method worked well and gave me excellent flavor and good heat. One warning though- the flavor remained stable, but the heat diminished a bit in the bottle, so if you want some heat, you might want to make it a bit hotter than you think you're going to want it if you use this method.
However, you choose to "pepper" your beer, I hope it turns out great! Enjoy!
