Drawing in hand-painted style require small changes in the way you normally draw graphics. You have to look around a bit for what works in each style.
If you would use real brushes and pens you would be probably guided by the same principles since the NPR styles tries to mimic the real methods.
If you need to use small text then you probably want to draw image bit larger than you would use and then shrink it and sharpen it later.
Small text may look unreadable or out of place while large text looks nicely shaded. There is also setting to make small text more readable by over-sampling the effect. In most presets this is turned on.
Use color transitions
What works really great for natural styles is simple Linear, Circular or Burst Color transition not only using different colors, but also different intensities. A perfect solid color across the object is more of a domain of the recent digital era, not a hand painted style.
Avoid Empty Background
Painting styles such as watercolor or paint are almost always best used on some solid or even better gradient object background as they mimic closely the actual technique. (object are hardly ever painted on a white background except few water color illustration techniques)
If some objects don't have enough details after applying the NPR style, put them in the Package, then open the package and resize the object to about twice its size. Close the Package then resize the package back to desired size and sharpen it with the interactive sharpen tool.
Using Feather Effect will disable creating object outline even if you cancel the feather effect by moving the sliders to far left.
Lastly, have fun and don't be afraid to experiment.