The advantages of a simple brush
At this stage I prefer to move fast and cover as much ground as possible. Disabling Pressure Sensitivity on my Photoshop brush significantly reduces my ability to create wellrendered drawings, because I’m forced to move from one thumbnail to the next at a quicker pace. I use a standard, Round 6px Photoshop brush, and turn off all its fancy features.
I stay away from proper perspective drawing for now. Instead, I stick to simple isometric side or three-quarters views for three reasons. First, drawing in perspective is hard and I don’t feel like it! Second, seeing all the designs in the same perspective makes it easier to compare them. Third, because all the sketches share the same angle and lens, it’s easy to quickly mix and match individual body parts: put one mech’s head on another mech’s body, take one mech’s arms and put them on another one… that sort of thing.