A quick tip for sculpting with Blender: if you use scrape and flatten brushes, the polygons and thus the texture won’t get distorted like they would with the smooth brush. Obviously there are limits but the nature of the smooth brush is to equalize the edge lengths which obviously will create the blurry patches you showed. Alternatively if you were to create a unifornmly remeshed version of your scan first using let’s say Zbrush’s dynamesh or ZRemesher the smoothing-distortion effect is also minimized to some degree.
If you didn’t alter the position/rotation/scale of your object at all in Blender you can copy the original rcinfo file and name the duplicate modelfilename.obj.rcinfo.