1. Bitmap Layer With Noise
Probably the most obvious method for adding texture to a shape is to
create a normal bitmap layer, fill it with a color, select Filter → Noise →
Add Noise, then apply a mask or Vector Mask to match the element
you’re adding noise to.
Using a high amount of noise, setting the layer blending mode to
Luminosity and reducing the opacity will yield the most control over the
noise with the least disturbance to the underlying layers. A noise setting of
48% gives a high dynamic range without clipping the noise. (Clipping
results in higher contrast, which might not be desirable.)