Yeah man, this is exacly what i mean. Use the first note of the vocal as a clue. Well, i think the best way to know if you are a on a right key is to play the vocal and the kick (in this case) in the same time. Now, when you hit play the first note of your vocal in loof you can hit the kick on a pad or a controller and listen to the right key. Just try it and you will have the right one in the end =)
After a couple practices it will be much easier to detect it and when you practice a lit bit more you will detect the right key just from hearing the vocals GOOD LUCK!
