Our pack does the following. The Pack provides a kit to every scout at the annual Christmas party and keeps a few in reserve. In January, a week or two before the race, there's a pack meeting where parents bring in tools and the cub scouts that need assistance bring in there blocks of wood, and everyone works for a couple of hours to design, cut, sand, etc. (everything but paint and apply graphite) to help anyone in the Pack that needs it. This really helped a couple of scouts that didn't have that help available at home.
Rules of the race are pretty simple: you can check in the night before or the morning of. It must be a newly constructed car. No pre-built kits permitted. If you want to use a vehicle from a previous year, if adults or siblings want to race, if you want to violate the weight restrictions, no problem! There's an Outlaw race that occurs afterwards. Our schedule is: race, eat lunch, give awards, run outlaw races.