I don´t understand the whole B spec. I thought it was for people like me, that don´t have 24/7 time to spend on this game. Now after a few races in the B spec I recognized, that you have to sit there and give Bob orders and watch him drive, what is very boring. Puls he didn´t manage to win the second SCup race with a full tuned FTO. So for me this mode is useless. BUT I read, that you can only drive the 24 endurance races with 3 other B-spec drivers. I don´t know if this is true but it would be a shame.
Put him in an fairly overpowered car and you can usually get away with not giving a single command.
The only exception I've noticed is occasionally on some slow tracks with a lot of tight corners (I suddenly noticed one of my guys was near the back of the field at Eiger Nordwand, despite being 150+ hp up on the opponents - there simply wasn't enough room on that track for the car to stretch its legs, and he was constantly stuck in traffic around those hairpin corners. I managed to get him to first on the remaining two laps with some increase pace and overtake commands).