The links below goes to three different solutions for lighthouse lighting, each differnt in complexity.
1 - The Simplest
Also the one that probably best resembles flashes, and the one used for my lighthouse.
http://www.kpsec.freeuk.com/projects/lighthouse.htm
2 - A bit more difficult
This circuit attempts to simulate the rotating optics gradually increasing/decreasing light before and after the blink.
http://www.discovercircuits.com/circuit-solutions/miniature-lighthouse.html
3 - The most developed and probably the most complex
This will also simulate the character of the rotating light source.
http://www.trainelectronics.com/artcles/LIGHTHOUSE/index.htm
Regardless of which version is chosen one gets a correct lighthouse light on the layout. The model harbour comes to life so to say.