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.

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

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)...

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.