You can get a roll of neutral density filter film for relatively cheap...I think I paid $6 and you can either place it over the contact frame. Makes dodging and burning tougher. If you have a cone or shade around the bulb, you could cut a piece of the film and attach it to the cone/shade/reflector. Raising the buld is a good idea too. Make sure you get even light on the neg.
When I print silver I use a 7.5 watt bulb in a small reflector. At the base of the reflector I attached a small frame that allows placement of 6X6" ND filters. You could also use VC filters in the frame.