Here is another good example of the polished finish that can be obtained on acrylic plastic using a barrel tumbling process only. The part on the left had been cut and machined to the general shape and size. The machining marks and square edges can be seen rather clearly - along with the dull surface finish.
A two-step dry barrel tumbling process was used to achieve the polished results on the right. Both steps used a Hardwood Media. The first step using Shynolyte Pre-Polishing Cream provided the edge rounding and a smooth (but matte) surface finish. The second step using Microlyte Polishing Cream brought out the bright shine and gloss of the plastic. Each step was about 24 hours and the results certainly speak for themselves.