The part will probably be marred and you could easily be hurt. This applies to buffing and grinding as well. A buffing wheel is made of cloth. By itself it is not abrasive. To make it work propoerly, abrasive must be applied.
Abrasives come in a tube and are suspended in wax.
The tube is pressed onto the wheel as it spins, melting the wax which helps the abrasive adhere to the cloth. To buff a part, hold it against the wheel with a firm pressure. Keep moving the part about and gradually lighten the pressure as the finish gets finer and finer.