Question regarding texture in 2D images
My question is related to applying texture in 2D images for concept art. I am a roughly beginner-intermediate skilled artist and it's something I've been really struggling with lately. It seems like I've viewed countless tutorials and tips, most of them recommending creating custom brushes (photoshop). This is particularly true if I'm trying to get the texture to match a theme (shiny, slick surfaces for sci-fi for example, or grainy bump textures for rough surfaces such as brick/stone) and I'm just curious if anyone has some tips or recommendations especially for an intermediate level artist.
What should I be focusing on, in terms of work-study or observation, to overcome this problem? Is creating custom brushes generally the best method, or does that actually slow down the concept process if you are creating brushes every time you need a texture?