If you have a corner or turn that makes it really awkward not to change direction, you can either color using curved lines or color using very small circles instead of lines. Just keep in mind that how you color will always be visible and will create the appearance of texture.
Professional level pencils like Derwent or Prismacolor offer the best quality and typically are the most expensive pencils to buy. The wax in these pencils is softer and the colors are a higher pigment providing brighter colors. The soft application allows blending and shading.