I used to use thread basting, but it would take me hours to removed it and it always seemed to get caught in my quilting stitches. My last quilt I made I used pins. It was fast and easy. I use a butter knife to help close them so I didn't hurt my fingers.
Yes, over 300 pins sounds right! I have 600 on hand so I won't run out. Better too basted than ripping out quilting because of pluckering!