The nitty-gritty if you're interested (I'm not sure if this makes sense ):
I put the head and torso on a layer just beneath the dress, with cutouts in the dress where the hair would show through. Then I used the smudge tool like heck all over the hair to make it longer So the hair is bigger than you can see since it's a layer below the dress.
The cutouts in the dress were pretty rough (the places where the hair shows though), so I used the eraser on the cutouts to smooth them out. And because I'd made the hair bigger in the layer below, when I used the eraser on the dress, the hair showed though So not only was I able to smooth it out, but I also ended up with much thicker hair than I have ever had in life