I’ve found brushing a black fondant cake with Vodka left shiny streaks on the cake which luckily I was putting silver stars all over so it disguised the mistake. I think shortening is the better option, you only need a tiny amount on your hands and rub over the cake.
However, for next time, the best thing I’ve found for rolling out dark coloured fondant that would be spoilt by a dusting of icing on the table to prevent sticking (as you have found) is the latest thing called The Mat. Just google The Mat and check it out. I bought one, it takes a bit of getting used to. You don’t need to use any icing sugar or corn flour, you just put your fondant between two sheets of food grade vinyl and roll away. I find you need a bit more elbow grease to roll your fondant out (and priming the Mat before the first use with a tiny smear of shortening on the inside of both vinyl sheets helps a bit) but you never need to use icing sugar to roll out fondant again. Remembering to separate the sheets to let a bit of air in when rolling gets tough also helps. best thing is, the rolled fondant can be rolled thinner than you would normally be able to get it and you can pick the sheet up with the fondant still on it and just place it over the cake… no more digging your hands and arms under the fondant.