Conclusions: Even blasting helps the final surface quality.
Additional shells (3 or 4) help keep the print sealed during washing.
After blasting, the matte surface is prone to absorbing skin oils and other particles, much the way an SLS print does.
The blasting grit will alter the color of lighter PLAs— the white took on more of a bone hue and the natural clear developed a somewhat murky color. The black PLA blasted to a very nice matte grey. (via 3D Print Finishing Technique for Improved Surface Quality)