To make it grow fuller is a tricky one, because technically that can't actually be done.
But what you can do is look in to using something like nioxin. It gives the hair a thicker and fuller appearance and feeling because it swells the hair fibres. What it also does is creates the perfect growing space for new hair, by cleansing the follicles - making sure there's no clogging.
This in turn can make the hair grow thicker as the follicle isn't full and squashing the hair-and then in turn making it weaker before it's even grown to any kind of length.
It's not a cheap product range, but it does work. The shampoo, conditioner, and tonic is a 30 or 60 day plan, you have to be consistent with it to see the results.
It's a commitment, as it is cosmetic and not medical.
So once you stop using it, the benefits deplete over time.
If you want a more instant, thickening product the nioxin diaboost is crazy good!
Literally makes it feel like you've got 1,000s more hairs on your head.