I bought a couple of their weathering stuff (aging filters, mostly), which should work simply by adding ont top of the existing paint to darken/lighten the base color.

I suspect due to the fact that they are water based, they do not spread over the surface; even if I mist them with an airbrush, they still pull together in little droplets, unless the surface is extremely flat.

What do people use to break up the surface tension? How do others find them for shading?

Thank you.

Don't know about True Earth specifically, but you could try adding a small drop of washing-up liquid from your kitchen. This usually does the trick with water-based stuff...

Dish soap will break surface tension. Experiment. A drop or two of soap in a 1/4 cup of water and add some of that mix to your acrylic paint. Just a thought.

I was faster

Yes, but Greg was a bit more detailed.

Thank you for both?

guess that your base is gloss... lay a coat of flat varnish and it should work better. Same for applying pigments.

Yes, lay a base coat of matte clear to give some "tooth" to the surface plus a drop of dish washing liquid to the shader to break up the surface tension. This will much reduce the tendency for the water based paints and/or shaders to clump up.

If you are near a store that caters to professional photographers you might inquire as to a photo processing product called "Photo-Flo". This stuff has been around for about 100 years, it's cheap, and it's sole purpose is to break up the surface tension of the water in the photo processing chemicals. This so the glossy photo prints do not spot as they air dry.

The Photo-Flo has the advantage of not adding any "suds" to the paint which just might cause other unwanted problems.

on their site you will find many videos and info on how to use their products and the owner is also active here from time to time with his models with the nickname "Ironwork" if I remember correctly...however, with certain products they recommend to slightly wet the surface before application

It is he who you must contact....

https://armorama.kitmaker.net/forums/269951&page=1

Wetting the surface is actually a really good idea. Thank you. Will try.

if you subscribe to their newsletter they always send you links to their tutorials that are many and well done