4001 0 0 10.0 10.0 sfline 4002 0 0 5.0 2.0 gridbox 4003 0 0 10.0 10.0 grooveThe text line is the name of the texture used, you can use other names if you like.
GRVed is not difficult to use.
What you need to do mostly is align the start and finish , then to save polys you can remove the blackness in the straights where the car does not brakes for example.
You can also adjust the lateral position to avoid that the groove polys cross the traces and cause weird effects.
This can also be done by varying the width in particular areas.
Try and experiment, after a while you'll get it.