I've tended to just draw them with my tablet lately, following a rough layer below as a guide. That allows me to change the coat styles as desired, from soft to jagged to silty points or sandbags, etc.

After that it can be vectorized and stroked as desired.

Another good technique is to get/ create a bunch of different scaled brushes made of actual cost outlines (I think there's a couple posted somewhere here) and use those to add and subtract to build up the coast.

-RobA>