In addition to the good advice already given:
One thing that helps to smooth out the sanding lines is to adjust speeds (if available).
Each time you change grit, start on the slower speed, than flip the ball over and go across the grain on the higher speed, change grit, go slower, flip ball and go higher speed, etc.
By adjusting speeds, ball direction, changing hand pressure, and using lots of water you can get pretty proficient in a relatively short time. Good luck.
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Lane Carter, Strike Zone Pro Shops - Salt Lake City, Utah
Brunswick Amateur Staff