dude, great picture... pleeeease tell me, what is your process of doing this kind of speedpainting? i speedpaint but the style that i do isnt the style that i actually want haha... it works, but its not what i want.. i want something more like THIS!!!!
A typical process really; block in major forms and then work the canvas as a whole, tightening what's important and leaving loose what's not. Some brushes are based on previous attempts at certain forms (rocks, cracks, rubble) which puts the "speed" in there. Good luck!