Too much rosin causes a raspy sound and makes a mess on the violin. Round rosin should be turned as you apply the rosin, as it wears the bow hairs more evenly. Rectangular rosin should be used against each edge and the middle alternately to keep the rosin flat hinder getting a groove and wearing the bow hairs unevenly. If you think you put on too much rosin, use a tissue to remove some. Four to five strokes every other playing time should be sufficient.