Painted the footprint by now.
Well, for painting, I used a mixing dish, water for thinning, some gloss brown acrylic airbrush color, Revell Aqua Color 'Dark Earth' (flat, acrylic aswell) and some brushes of course!
First, I thinned some 'Dark Earth' so it has the same viscosity as the airbrush color (like milk) and painted one layer of paint on the epoxy. Next, painted the the inside of the foot with the gloss brown color.
Well, that's about it.
Why I thinned the Dark Earth color? With a high viscosity, the paint isn't fully covering the epoxy, resulting in some shading of the surface, plus it results in far less (or none in this case) brush strokes, after it dried.
Satisfied so far.
What's left is to mount the, still to be weathered, foot onto the base, which will be done next.