Try rolling your fondant out onto cornstarch instead of sugar. Any that is showing once the cake is covered can be brushed off with a soft paintbrush. If you have cracks you can try making some royal icing in the same color of your fondantant and piping it over the cracks with a very fine tip. Then using a damp paintbrush or your finger, wipe away the excess. The royal icing will fill in your cracks and they will be less noticable.