Sand paper is your FRIEND!! It can make a huge difference in fine details, and helping you to create a sharp edge. I use grit ranging from 120 to 380 grit. The higher the number, the more fine your sandpaper is. I use 120 to sand edges and shape, and then I follow behind that with a fine grit to remove sanding lines.
As you can see in the image above, sanding allowed me to sculpt in the "bones" of my bat wing, and then create a crisp edge that made the wing more realistic once it was painted. I also use this trick when sculpting clothing on my art dolls.
Crisp edges on Steampunk Goggles, Sharp corners on hats, Clean and Straight Trim on waistcoats.