We left the map at the end of part 1 at an adequate state; but the image was generally a bit flat.
So, I decided to add a few more layers into it. Each of these providing a bit more information and visual stimulus.
First, immediately below the "sandy beach" layer, I add a "wet sand" layer.
When a material is wet it tends to be a bit darker, and a bit richer in colour (I could get into the properties of physics that determine this...things like diffraction of light and scattering of reflection from rough or smooth items, but just trust me on this for the moment). The layer style follows cues from the sandy layer, with a pattern texture of "yellow mums" at an opacity of 100%. To draw this layer I use an airbrush style of brush, big diffuse and black (colour doesn't matter because everything is going to be overlaid with the texture).
I spray along the coastlines where the beaches are, giving a vague impression that the sand continues down from these areas an into the water. I make sure not to spray near the rocky outcrops, because these are more jagged rocky drops rather than soft sandy borders to the island. The beach to the maps west is done with the size of the brush dialled up even more and the opacity turned down to 25% or so...it takes a few sweeps to get a look I'm happy with.
Using the same vague technique (new layer, new texture, airbrush to mark out the layer), I create the deep water around the island. There is a "waves" pattern overlay and that comes pretty close to what I want for this map, but the colours are a bit too harsh compared to everything else on the map. Instead of turning down the opacity of the pattern overlay (which would expose the colour I've been using to mark out the layer), I turn down the opacity of the whole layer. This blends it in better, and allows some of the colours from the shallow water layer to seep through.
Toward the south of the island, I make sure to indicate deep water heading into the secret dock of the island, that's the safe passage for Isabel's ships to get in or out.
Next I move away from the water and focus on a new material for the map...the wood. This applies to the ships, and the piers running across the islands interior waterways.
In a new layer just under the drawn map I mark out the wooden areas using the polygonal lasso. Each of the wooden areas it bucket-filled with a woody brown colour. I'm in a hurry here and it give a bit of contrast...so it works at a pinch. Using the same colour I spray a few clusters of wooden items that have been drawn into the maps (I promptly forget about these later...I had intended to make these items stand out in their respective rooms, but something didn't quite work and they just ended up getting covered by other textures).
That's about it for the flat layers of colour. The map is looking a bit more interesting, but still a bit flat...and that's where a distinctly different technique comes into its own.