There are a lot of ways you could do this. You could draw a "temporary" solid (or hollow if you prefer) polygon or fractal polygon to represent your continent as a rough outline, then use the drawing tool for creating the continent when you are ready to draw in detail (perhaps on it's own temporary sheet). Or you could just draw a path or fractal path for areas you want to detail now and then when you are ready use the continent drawing tool. In all cases where you have an area pre-drawn that you like, you can use the Trace option with the continent drawing tool to copy that bit of coast into the final continent.
When you are done just delete (or hide) the temporary continent/coast lines.