Honestly, for the amount of precision you are seeing, Photoshop brushes are not the proper tool. You could use the Shape Tool to draw a line, then manually add points with the Pen Tool to alter segments of the line. Or you could easily use Illustrator CS5 and it's Width tool on lines. You're asking Photshop to be precise where it's never been designed to be that precise. A brush is just that.. a brush, not a ruling pen. Grab a real life brush and a piece of paper and try to be as proceise as you are asking. With some practice you can get close. But the nature of the tools themselves aren't best suited for high-recision work. The below was created using a brush, the shift key, and shape dynamics via a Wacom Intuos 4 tablet. To create the angle, rotate the canvas (assuming yorur system supports OpenGL features) so you're drawing perpendicular to the document window. The shift key will contrain based on the document window, not the actual canvas. Or draw your strokes perpendicularly first, then rotate them to the angle needed.
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