its the hard edge brushes in photoshop usually. or create some block or triangle brushes. pple tend to use brushes digitally to softly. i block in alot of my work and at some stage it looks similar to these pieces. so, same technique. if you work with a high level of opacity you will get these type of results quite quickly as well. sometimes masking and selection is also required. building shapes and dropping colour in and working with layers ontop of that will also help. obviously what i am mentioning here is very outline based.
Thanks for the info. I need to start using some of these because end effect is goddamn amazingI think Dave Rapoza is using similar techniques.
p.s. As I'm using PS rater occasionally these days I'm wondering that it could be achieved in GIMP, Krita or MyPaint... probably it gonna be pain in the ass but there is no progress without struggle... I think Thanks again.