Collect fees for the pool from all players before the first race begins. Allowing players to stay in "on good faith" presents the risk of them having a poor start and electing to drop out without paying the entry fee, essentially giving them a free chance to have a good start.
Create a pick sheet for every race in a spreadsheet program, featuring a list of all of the drivers competing in the race, and distribute a copy to every participant in the pool. Distribute the sheets via email or by printing off a copy for each participant.
Instruct the participants to select one driver whom they have not selected previously this season as their driver for the race.
Gather all entry sheets, or at least get the names of the drivers selected by all of the pool participants, prior to the start of the race.
Score the race after its completion, giving every player points equal to the Sprint Cup Series points earned by her driver.
Update the standings in a spreadsheet file by adding each person's scores to his season totals, so that participants can track their standing in the pool.