Go to Avids website, $1 metal, rubber, or hybrid shielded bearings. I would only worry about the hub, and knuckle bearings. Get $20-$30 worth. Drive the car for a few race days, and just replace as necessary. At $1 apiece it's easier to replace than to take the time and annoyance of cleaning. If you have a car with DCJ's make sure you get a few 5x8x3mm bearings for the inside of the front knuckle. But the 5x8x3 only come in metal shielded from Avid. I bought $40 worth a year ago and have used less than have of them.

Good luck and have fun.