Need Advice; Want to Achieve Leather/hyde Texture

In past projects where I needed to achieve textures to simulate hair or hides, I've used a hot knife tool that I picked up at a Michaels craft store. It has a temperature control setting that allows users to dial in an appropriate heat setting for consistent results. Because every kit manufacturer uses different plastic, I first try things out on a piece of the kit's sprue to get the temperature I need. From there, it's a matter of carving little lines into the surface of the model. Little C and S shapes would probably work best for animal hide, while a combination of straight and slightly wavy lines work well for things like manes, tails, and hair. A light sanding to even things out and it's off to primer.

That kit is apparently a re-boxing of the old Aurora Bison kit.   Just to clarify for the others, It's already molded with a textured coat.

I would use a base color for the coat and then lightly-very lightly-drybrush a lighter shade of the base color, to highlight and pick up the molded texture of the coat.  You could also go the other way, and use a light base, and then use slightly darker washes to emphasize the relief, leaving your base color as the highlight color on the high points.  Either way, with this kit, I would try to keep it as subtle as possible.

If you need to fill any seams, pay extra attention to KnightTemplar5150's advice.  Puttying will probably obliterate details around those seams, and you'll want to recreate the detail of the coat in those areas.  As he describes, you'll need to scribe or sculpt those lost details back in.

It's a great kit, though, and I look forward to seeing your build.