The Paint module does not differentiate between tools which work all the time, for example an airbrush, and those tools which depend on motion for their effect, such as chalks and pencils. Instead, in tool settings there is the entry "Start Painting after..." which makes possible much more flexibility in settings; in addition the movement dependency for movement-sensitive tools can be varied with this parameter.
With strongly covering tools a distance larger than 1 can well be entered here, but with the airbrush and similar tools the distance must be 0. This means that the tool will still be applied even with the mouse at a standstill. In this case you shouldn't select a high intensity, otherwise a a very fast rate of coverage will be applied which will be difficult to control. There are some examples supplied in the tool parameters file for this as well.
