This looks good.The fact that is actually a clean draw, makes me think that animation with that... Tool that makes sprites look bit blurry due the pixels work here.
as for a tutorial, that takes a bit of time. But to make it short just max out the resolution to 300 or more depending on your pc.if you have a tablet or a screen tablet just draw over the sprite with an outline. Then reduce the size in Photoshop using bilinear resample back to the actual resolution. Lastly paint it in base colors add the shades.
Working on him all week , still like the original art sprite from Pyron. But for now that's way out of my rage knowledge.