I've tried a new technique of brush and want to know how is it, I know that the car has mistakes on the roof and the right part of the bumper, but i can't do this Subaru more...

The brush on the hood is bad.
Not bad chop but toony.

Hey GGG. I see what you've tried to do. I'd personally not use this technique when brushing.

I like to select the entire car and fill it with colour on an empty layer, then select all the black parts like vents and so on and fill them with black. Then use just white and black on separate layers to create shadows and highlights.

Edit: HERE is a tutorial made by jackdarton. Have a read.

I'm not saying that this is the way to do it, I'm just saying that it's one of the ways to do it and personally my favourite.