I love using the liquify tool to enhance hair (and to reduce post-baby tums for when requested by a mum). Below is a before and after of an image.
I used the photoshop Filter>liquify tool to make her hair a little thicker each side. The advantage of the liquify tool over the warp tool is that you don't get any joining gaps. it's completely undetectable if you use a large brush to keep the curves smooth.
I also used the dodge tool to pull up the beautiful highlights of her hair and pumped up the saturation by +8 isolated by a mask to bring out the chestnut colouring.