Hi, It was quite easy for me in fact.
First of all, my B-tard was a level 27 when I done it.
Standard Specs, just a touch in gear ratios. The 250mph/400km/h set up is quite nice except for Cote d'Azur. I kept the Hard tires.
It's a Push - Overtake babysitting until the first place. Then you babysit it for a while, to build a nice gap, then you can leave it. I babysitted for most of the time while I was doing something else in my notebook.
Pitting, well, because of fuel you would have to pit somewhere in the last 3 laps, except Cote d'Azur, where you can do the whole race without pitting, same as the AI cars. Usually I would build a comfortable gap to join the race, after pitting in the lead, and then pitted near 2/3 of the race, then don't bother any more for the rest of the race, has IA cars were beyond Bob and still a pit stop to make. If they came near him, they automatically would make him push a little hard and up his pace. Has they only pit to late in the race there is no danger of a comeback.
Only lose one race, at Cote d'Azur because it was constantly spinning at Casino's corner, my bad, I wasn't paying much attention and after 8-9 laps I realized the problem, Bob was 11th!!!, I thought "let's calm down", overtake this slower guys and join the front group, then pace down to make no more spins and try leapfrog them in the pit stops, I just realized to late that there was no need of a pit stop and I couldn't overtake them all, has not touching gear ratio didn't help either, just tooooo loooong for this track.