Here is Arts I made for my big article about making and using custom brushes for a book
Master the Art of Speed Painting: Digital Painting book published by 3Dtotal.
This top art is also on the cover of this awesome publication
Book is also filled with outstanding knowledge of James Paick, Florian Aupetit, Ioan Demitrescu and many more.
also check my gumroad site for brush packs and stuff :)