I think that is one of the bigger misconceptions around "working the ball," specifically that it is a skill you should only start working on once you can consistently hit the ball straight. Thing is, nobody consistently hits the ball straight. The idea is to reduce the margin of error in your shot. In other words, if you try to hit a draw and you aim down the right side of the fairway, chances are you will go left, worse case straight, but you are not very likely to go right. In my opinion, once you start making decent contact on your swing (i.e. you're not too worried about whether you will get the ball in the air), you should start trying to learn to put a little draw and/or fade on the ball during your practice sessions.