Try to leave a small amount of starter wort in the flask when decanting. Then you can swirl it into the starter to make it thinner. This makes the yeast slurry a little thinner and easier to pour. If the yeast is too thick, then add a half cup or so of wort to the starter to thin out the yeast prior to pitching.
"Give a man a beer, and he will waste an hour. Teach a man to brew, and he will waste a lifetime!" Bill Owen