Practically you can stick small pieces of tape to the parts where there are not much features and have it perfectly tracked or scanned .
I am actually using cubes for that , some also have magnets that can be stick to metal surfaces .
Or additional elements around the scanned object for better tracking
This subject is about tracking while scanning not alignment after scanning .
For alignment I use color mode , I paint mini blue dots on the surface where there are no features if I scan multiple angles separately , and later the RGB data allows me to align the fragments perfectly based on the dots in Revo Studio or CC.
It is better as you don’t have to deal with bumps and holes on the surface .