You can probably use a different foot but the darning will give you the best result because you can see where you are going. I don't think the darning foot goes down as far so it doesn't have as much pressure. I'd check on the price of purchasing one.
More important than the foot is be sure you are dropping your feed dogs for free motion. They will pull the underside in one direction and you may be trying to pull it in another direction. If they don't drop you can tape a piece of sturdy plastic over them.