Sure, depending on the medium I either mix my own skintone or use a premade one. My skintones for white skin are usually a really light orange to reddish orange to a very light pink for fair skin. Once I have a base in color in place I usually do a first base layer of a darker (darker then the base, but not much darker) reddish orange, which I sometimes mix with blue, I usually continue shading with a mix of violets, cool browns and blues. Just keep in mind that shadows are cooler than areas that have been hit by the sun.Give those areas a warm orange glow when you want to show that it's sunny.
My refining of artwork is really just going through the steps I deem nessesary for said piece to be complete. I draw a pose very loosely,a concept of an artwork, I think about a background, will there be more characters in the background, what do they look like, are they important,what perspective angle do I want to take? It's like your eyes, when you are looking at someone, you are really only looking at that person, the background is pretty blurry, so while the backgrounds are pretty important, if you have a portrait, no one is going to pay attention to the millions of little details you put behind them. When drawing a building, you are only looking at that building, the people aren't important, you can draw them like humanoid blobs. For me, when I have done the base sketch I like to make a detailed sketch on top of the mostly geometric shapes a stick figures I used to make the base sketch (this second sketching phase takes the longest, usually two or more hours, since I pay extra close attention at the anatomy of my characters and the perspective). After I have done that I usually ink it, but sometimes I like to paint so I'll do that in grey scale and add color on top later, it helps me to keep my values in check. Or sometimes I color in grey scale after I've done the line work if I want more dimension and depth in a piece that I think is overall too light, or looks weird. I think that it's best after you've done your line work you apply the base colors to the whole drawing, if you work on one thing at the time and then later try to match the rest of the picture to it you'll find that it doesn't fit together at all and looks weird. If you take a look at my latest deviation, my icon, you can see that it was build up in layers. First I put all the base colors, then, I added the first layer of shading to the whole image, then after that I added the second, and finally the third in the darkest parts. Once that is done I add highlights to place that either catch the light, in this picture the top of her head, or areas that are reflective, like someone's eyes. Then sign it and I'm done.