Picking two points on the 3d model surface to measure distances I'm a blender n00b and this may be a wrong tool for the job, but I've found some great features in Blender (like the caliper add on), so I'm pretty sure there's a way to easily (or at least bit easier) select two surface points of a loaded 3D .ply model somehow instead of moving the caliper/ruler points and its x y z axis individually one at a time?

Is there such a tool in Blender (or anything standalone) for selecting points from a surface of a loaded 3D model and measuring the distance of those selected points please? 

Any explanation for how to do it any faster in Blender, instead of moving x y z axis of caliper (or ruler/protractor tool) one at a time attempting to align them to a surface of a loaded 3D model, or in any other tool that's able to measure that would be greatly helpful and appreciated. TIA
My favorite tool for measuring things is the measureit addon.

Once the addon is installed and enabled, simply enable Show in 3D view > Tool Shelf (T) > Measureit tab. Then select the vertices you want to measure and click Segment. You can edit and delete individual measurements in the Properties Region (N):