Hmm, Finnish doesn't have the instrumental case, but Hungarian, another Uralic language, does. Finnish tends to prefer the adessive for the same purpose. I'm not sure why the difference between the instrumental and instructive per language family, or indeed what that specific difference might be.
vihdoin (adv) finally vihdoin (v) first-person singular indicative past form of vihtoa, to whip (specifically with the following) vihdoin (n) instructive case, i.e. "by means of", form of vihta (a kind of whisk made of birch twigs and used in the sauna to enhance the effect of heat by gently beating oneself with it)