I do Time trial, set official day time with car which i have in the career and i go usually 10-15 laps (until i go consistently) and get the fastest lap. Then i go to grand Prix mode, set no practice, short Q, race doesn't matter, clear weather. I only accelerate time (haven't tried to skip the Q session) until the end of the Q to results. And my TT fastest time should be where i actually want be. Usually looking at my teamate's time in the Q results, which should be similar to the mine one from TT. At least for me it works.