And then you've got me and I prefer to make a potent extract directly in vodka and use that extract instead of soaking the beans in a weaker alcohol solution and making a less controlled extract.
But this is one of those places where Denny and I disagree.
It's definitely easier to get the right dosage using the extract. Just add to the finished beer til it tastes like you want it to. But when I've tried that, I swear I can always detect the heat of the vodka in the beer. I'm more than willing to admit that it may be strictly in my head (oh, so many comments to be made!), but I've found ways to avoid doing that. Either technique works well, so do whatever you think is the right way for you.
The best way is a compromise of both methods. Put some vanilla beans or coffee or whatever else you want to extract into a coffee press, fill with the beer you are going to infuse, refrigerate the press for a few days, press the knob down, taste the extract, then dose the beer.