Yeah, I do 'digital realism' as I call it, (digital painting, hair by hair, and not only that, but painting the highlights and shadows of each individual hair for a look of 'depth') so I know the whole 'time consuming' aspect all too well, having spent 200+ hours on pieces before. It's great though when you fall into that 'zone' and suddenly 6 hours of work flies by and seems like only 30 minutes. And yeah, I rarely use custom brushes either, I tend to paint everything in manually. It's tedious but it gives you the most control over variation and helps make things look natural. Custom brushes are good for small textural things, but things like spots or other markings which would curve and bend along the figure's body are best done by hand ;) (even if it does take forever!)

And yep, I've done some gradient shading in the past, many many years ago, but never to the extent that you have done here. I tend to digitally paint most of my stuff (I like smearing colors around and being able to give it that stylistic, loose look now and then).