How can I decrease friction and add traction to my mousetrap car?

I have used graphite as a lubricant. My back wheels are CD's and my front wheels are pinewood derby racer wheels. As traction, we were going to use foamy double stick tape and put sand paper over that. Does that sound good? Our car goes a litlle over 6 meters... How can we improve the distance while not dramatically altering our design. And don't say increase the axle to wheele ratio because i already did that.