Made some last fall. Two 1.5 liter bottles Smirnoff Vodka. Don't need real good stuff. About 12+ beans in each. Sliced the beans lengthwise and dropped in the bottles. Kept out on the kitchen counter. Shook bottles daily or whenever we thought of it.Kept getting darker as time went on. We let it steep for about three months. WOW.... good stuff. Put it in 1/2 liter water bottles and keep in cupboard. Going to start another batch soon. I am going to try a bottle of Bourbon this time also. I also read that the longer it steeps, the better it is. Also read that you can use some from the bottle and replace with fresh vodka and keep steeping it. Add additional beans as time goes on. No need to throw remainder away. It is in alcohol, it shouldn't spoil.
Good luck. Let us know how it turns out...