Usually when I draw characters, tools, weapons and etc. I start with doing silhouettes, just doodling with a thick brush to get a shape to work with. When I find a shape I like, I start to "block" out highlights and such so I can tell what is what. Then I just start to play around with the design, looking at references and such.
If you wanna paint environments, it's basically the same method though I make a really quick sketch on how it should look, then I take the lasso tool and draw some shapes, filling those with different color values depending on how far away and how close the objects are (darker colors for those which are closer and lighter for those further away), It all depends on perspective.
Using different brushes is one way to make the things you draw look better, but brushes doesn't make an individual better at drawing in general
