In Career mode, select either a short or long race weekend (long will have 3 practice sessions, short will only have 1) and drive around the track in practice. A track such as Monza would be the quickest, as there are very few braking points. If you only did Monza, it would take about 3 hours to cover 805kms. You may want to mix it up though. Use the time in practice to test out your car settings and try to improve upon your laps to keep things interesting.
Alternatively, you can do 10 laps on each track as you make your way through the season. This should see you unlock the achievement without too much monotony.