I've always said that B-Spec Mode is for GT gamers who either aren't very good or just want to race without any actual input. You'll want to be very preceise and careful in your racing. Your AI racer is your little glimmer in which you must make it your superstar.
Being a sports fan, I normally see all-access stuff about coaches rooting on their players to do their best. I can recall seeing Pete Caroll coach his USC Trojans to a National Championship in college football. Can recall Coach K instruct his Duke Blue Devils to take down all opposition on the hardwood. And basically, this is all what B-Spec mode is. It's about coaching. I guess a good way to have fun with this mode is to pretend you're the head of your team in a sport of your choice (American football, football, rugby, basketball, baseball, hockey, whatever). And your job is simple- tell your racer how to win the race. Give it the car, the settings, the opposition, and off you go.
Now for my advice on B-Spec. Not to make anyone feel offended, but if you stink in A-Spec, you'll probably be bad in B-Spec as well. It's all about how well you can make something of nothing. Remember to stay focused and optomistic. If you know you're not going to win the race, don't lose your focus. Second place isn't always the first loser. Just remember to win the race rather than dominate. The more you're able to be "silently aggressive" with B-Spec mode, the more you'll win the race at hand. Having said this, this is John M. of Houston, Texas, USA signing off. Good day/night.