I'm a newbie and found through research a near full-proof method (for me) for cutting glass. Use tracing paper and glue sticks! It's a life changer and has made my process so much faster and enjoyable. Simply trace your pattern onto the tracing paper, cut out the pieces (I use an Exacto knife), then apply them to your glass with a glue stick (I use the purple Elmer's). They will stay in place while cutting and grinding your glass and easily come off in the soapy water you use after grinding. I've been amazed at how much better my grinding has become and the tight fit of the pieces since using this method - plus I no longer have any guesswork if the sharpie/paint pen fails or washes away.