I use boards (not that I always hit 'em you understand). There are some synthetics that are very difficult since they are uniform in color, but on wood or most synthetics there is variation so you can pick out a discoloration to aim at. I vary the depth of my aiming point depending on how dry the lanes are; closer = wetter.
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"Things fall apart; the center cannot hold; mere anarchy is loosed upon the world,"
I'm Ragnar Floggurass, and I approve this message