With hitting the apexes, there is a saying when shooting, "Aim small and miss small", in other words watch the apex and aim at a point on it so you hit it exactly, the more you concentrate the better you will get. If your overshooting them your too fast.
After playing the Race Driver games back in the day I used to roar up to corners then slam on the brakes then try and roar off again, in GTR2 if you do that the other cars will leave you in their dust, you have to slow down before the corner, then accelerate through the corner and don't give it full throttle until you can leave it there without letting off again until the next corner, think smooth not fast.