Now we have pretty good background for our future waterdrops.

Condensed - Making Of - Step 6

Now the fun begins - waterdrops. Create new layer, fill with white, and then in another new layer (!) draw a slighly chaotic oval using sharp pencil tool. Remember, nature never has ideal shapes, so dont use vector tools.

Condensed - Making Of - Step 7

Now spent about an hour or two and fill entire document with drops outlines.

Condensed - Making Of - Step 8
 

Good, now we have waterdrops outlined, we need to fill them with black color. It is very easy - with magic wand, click anywhere outside waterdrops (make sure Contiguous is checked)...

Condensed - Making Of - Step 9

then invert your selection (Ctrl-Shift-I) and fill with black color using Bucket (G) - make sure Contiguous is NOT checked, or you'll have to fill each waterdrop manually.

Condensed - Making Of - Step 10