Dodge & burn are meant to be used subtly. If you set it so that the effect comes quickly, then it will also obvious and unnatural looking. I use settings of:
Size: As needed
Hardness: this controls how hard or soft the edge of the effect is. I use a fairly soft setting to keep the look natural. Keep it below 50.
Steps: About 10 (I use this setting for all tools, if you use too little or to much, the cursor will either be jerky or it will follow you so slowly it is unusable.)
Opacity: I normally use 3. The larger the number the more obvious the effect of the brush will be. I rarely use a setting greater than 5.
Before starting, duplicate the layer and work on the upper one. This allows you to turn the layer on and off to compare it to what you started with.
Repeatedly go over the area to be lightened or darkened. Some sloppiness is desirable, as it keeps the effect looking natural. You can see the dodge brush in my above screenshot, being used to lighten the woman in the chair wearing dark clothes.