It all depends on what medium you're comfortable with. It's nearly impossible to do a tutorial step by step as it's a very long and tedious process when done correctly and again the color you're doing, materials you're using, model you're using, material of that model, and medium you're working in all makes the difference.
I use pastels, it's a medium I feel comfortable with using however it can be difficult to grasp for some people.
I would suggest starting out with acrylics, it's the cheapest medium you can use and is fairly easy to use.
As a quick run-down you'll first want to wash the model very well with soap and water, then let air-dry for at least a few hours. Make sure that model is clean with no dust or dirt. Once completely dry - and make sure
it is 100% dry, spray light, thin coats of primer in your color choice (will depend on what color model you're going for) until it's solid. I like to hold the model by the tail or a leg. If there are still seams or parts of the logo showing, sand it down and re-prime. Fill in any air bubbles and sand out rough spots. I always say that a poor prep job will kill an otherwise good paint job. Prepping isn't hard - just incredibly boring.
I like to start off with an acrylic basecoat on each model I do - it's a mixture of water, water, white gesso, and white acrylic paint, thinned down to a milky consistency. That's painted on in a few thin layers until everything is covered. You don't have to do that but I like how the pastels stick to the acrylic basecoat.
From here it's hard to explain anything else - as for pastels you'll need to mix up the color for the first layer of color, depending on whatever color you're going for, apply to the model in all areas. Be careful not to get too much in one area - you want a nice, flat color. Continue to apply color until the color you want is achieved. Always
work from a reference and never paint off an image in your head!
In between pastel layers you'll need to seal the model unless the pastels will rub off. Let each coat of sealer dry at least 30-45 minutes before doing the next layer of pastels, or you'll risk the model going tacky or crazing.
Keep in mind that using many layers of pastels is not uncommon, I use nearly 50-60 layers on just one horse most times. Start very light and do thin layers of pastels - if you add too much dark all at once the finish will become grainy.
Now all of that's for pastels, it'll be completely different if you're using another medium.
Hope that helped a bit!