Could anyone by chance explain to me how I make this curve on the car in photoshop please? I've been attempting a go at this for about an hour... I've tried about 3 different ways of making it, all coming up with really pixeled edges and just looks like crap, otherwise the end doesn't come out flat to the back... 

I've been wondering the same thing, I wish I knew. 

Could anyone by chance explain to me how I make this curve on the car in photoshop please? I've been attempting a go at this for about an hour... I've tried about 3 different ways of making it, all coming up with really pixeled edges and just looks like crap, otherwise the end doesn't come out flat to the back... 

Honestly, the best way that I was taught was to use the "Pen Tool". I would do some practice or even look up some videos on Youtube to find out the ways of the pen tool.

Pen tool, pen tool and more pen tool.
https://helpx.adobe.com/photoshop/using/drawing-pen-tools.html

I agree, pen tool to get the shape and gradient tool to get that color change.

Something like this:

 rock_county.psd

You can select the pen path by holding Ctrl and clicking on it.