stamp() would be a better way to go?
You can make a brush.
private var _brush = new FlxSprite().makeGraphic(2, 2, 0xFFFF0000);
canvas.stamp(_brush, Std.int(totalTime % 128), Std.int(totalTime / 128));
I know it's just to test, but the math you're doing limits the x, y to 0, 0 the first 2 seconds, and 0, 1 until 5 seconds, then 0, 2 after 5 seconds, etc. Std.int() floors it. So it takes over 10 seconds to get to 4 px. Over 1 minute to get to 28 px, so not so rapid, and only the left edge. The modulus % always returns the remainder, so that one is always going to be 0 since Std.int() floors it.