What exercise you can do to get better at drawing texture?

[darktiste]

As you're working traditionally, I've followed a lot of artists that suggest to think of texture with form, not as a last treatment which is how a lot of digital artists operate.

I gave away a really good book on this but I guess resources depend on what you want to learn. Seeing texture in forms as you build your structure, thinking of it in terms of different surfaces and how they're perceived through light, bringing it into focus, or are you after the technical aspects of rendering specific textures?

You can always cheat with photo editing software but it's worth experimenting with other mediums. I only like to use PS for colour and atmosphere. Textures added in later look obvious and enter that uncanny zone because it's not built around form, it's just a coating almost. Texture brushes are wildly overemphasised in digital art. A great way to make a quick splash concept but not always accurate or appealing.  

Before trying to answer if there are any other ways, what exactly are you doing now to train yourself in textures?

I am doing scale like those one to be able to apply onto any surface with no particular project just to train myself to be able to create appealing not over rendered texture not over simplified texture trying to find a good balance.Going from chaotic to orderly and from dark to light also going from small to big.Also like you said to be able to create texture that wrap around a form in a realistic way if possible.