AKVIS Watercolor supports the Batch Processing feature that lets you automatically convert a series of images with the same settings and saves you time and efforts. It is useful when creating a number of illustrations at the same style for a booklet or when processing all frames of video.
Even if you've never used this feature before it is simple to learn!
If you use the standalone version of AKVIS Watercolor, read the instructions here.
If you use the Watercolor plugin in Photoshop or other image editors, follow this tutorial.