For using Silicon, it's pretty much the same as described in that article, using a base color at the bottom and having the color come through the clear silicon. In addition, I used a clear blue to put some color difference in the crashing waves to the beach and white for the crashes all through an air brush. I also use a clear semi gloss coat on the water body away from the beach and blended where the waves are more torrent where the waves comes in or smashing up against the rock.
When you lay down the silicon, let it dry a little (like 5 minutes) and using a sculpting knife you can kinda mold it.
What I was doing was making a beach about 2 feet wide and about 10 feet across for my gaming table. Is was for a space marine campaign for 40k where we were storming a beach. Kinda a tribute to D-Day kinda battle.
I don't have it anymore or I'd take pics. A friend "borrowed" the 2x2 tiles and never returned them and I've been out of wargaming for years now.