Power assist off, I use force feedback on 7.
Took me an hour before I started to improve my lap times from the controller.
Biggest thing is : realise you are using a wheel, don't jerk the wheel back to neutral after a corner but ease it back, less dramatic weight shift for the car (controller suffers from that alot) = easier to control the car.
Also realise that you have pedals

Ease in the brake just like with a real car, don't just slam it down you'll lock up the wheels.
Same with the accelerator, 'feathering it' (god that word sounds obnoxious) allows you to hug the curb on long corners or follow the racing line better.
I think it's much easier with a wheel (apart from counter steering which is easier with the controller, mostly because of the steering assist that you can turn off with a wheel).
you'll automatically drive more smoothly and more tempered, which automatically makes you more consistent and improves your lap times.
The force feedback is a good indicator of understeer, if the wheel is heavy to turn then you are trying to turn too fast.
Don't get hung up on trying to push it right away, just enjoy the driving and turning into a corner with a wheel and playing with the pedals.
Buying a wheel won't magically make you better from day one, just like giving some cod shmuck (not a stab at you

) a mouse won't turn him into fatality instantly.
Doesn't mean it aint alot more accurate and alot more enjoyable.