A mild grit blasting, if done properly, will enhance the shot peen properties by removing some of the damage caused by the surface dents. Honing or lapping the surface after peening is another similar practice which helps to remove the surface damage caused by the peening dents. The residual stress remains, that's good news. The opportunity to remove the damage of the dents,is also good news. Just don't grit blast so aggresively that you erode enough surface to relieve the compressive stresses.
