Going through the entire car just before a big race is done at home because of the time needed.
I rebuild parts of my car while at the track. Clean and re lube all bearings, axles, and shocks every other race day. One day the front, next day the rear. Check and replace belts as needed. Clean pulleys every time I get the chance. Gearing and setup is done at the track during the day.
I have spent the last two days trying to lighten up my car but that is because it was way over weight for my next big race. I normally don't have to do this.