How to make terrain brushes?

[kinorunner 0]

Hi all, I'd wish to create some custom brushes for terrain detailing, as those from Paeng, Jeronji and others.

More exactly I'd try to make an aerographic effect to apply, for instance, snow or grass with a subtle, scalable stroke.

Even better if the brush is settable in size and strength- and, naturally it must be saveable.

First ( lazy ) attempts with Ilives to edit some existing brushes ended in nothing, I will definitely deepen the study some day but, without some guidance or hints, it seems a hard slope.

Are there posts or even tutorials I missed in my search?

Thanks for the attention