A quick and simple way to texture your bases in a swamp / toxic waste style
Apply Plastic Putty using an old brush. Swirls it around to create a texture like you see in the image. Make sure to let it cure properly before proceeding to the next step.
Apply Agrax Earthshade in several layers to build up the color to the desired shade. Make sure to let the wash dry between passes, and make sure not to "overbrush" on each coat, or you might accidentally remove the previous one.
Paint the areas where you want the pools of toxic waste / green water to be using any shade of green. You can make it as dark or as bright as you want. This will make them more or less saturated.
Apply Nurgles Rot on top of the areas you previously painted green. Do as many thin layers as you need to build up the colour.
Optionally, do a coat of gloss varnish over the areas painted with Nurgles Rot