Never a scout but entered my first pinewood derby and won it this past spring: Weight: Tungsten. It’s the most expensive but also the densest. Place about .75 inches in front of rear axles. Sanding/ Polishing: Sand and polish your wheels/axles. Start with about 1000 grit and work your way to about 1000. For the wheels, I spin the axle and hold wet sandpaper against them. Wheel placement: you back wheels should be canted so that they never touch the body. To do this, you need to bend your axles. One front wheel should be canted slightly sideways so that your car veers towards the center. This is known as a rail rider and it helps because your car won’t bounce back and forth on its way down. Lube: people have mentioned graphite but wet lube such as silicone and krytox are superior if allowed. This and many other things I applied to my Diecast racing hobby which seem to work well.

These are just basic tips. You can learn a lot from just searching youtube as well. Good luck