Bedding the rail is not necessarily a simple deal. I have my local smith do it as he has the necessary tools to do it properly. A simple explanation is he jigs the rifle up in his mill straight plum and all that stuff and verifies the receiver is correct and or fixes any problems then during the bedding process he verifies the trueness of the rail to the receiver with a dial indicator.
You know it's money well spent when mounting a new scope as I just did centering the reticle allowing for the 10 MOA slope in the rail and having it within a few clicks of dead nuts on the final sight in. When I removed the old scope there was not a ring mark on it. Seekins rings
Near rail and a smith bedded rail and the rings were not lapped as it's not necessary when the rail is properly mounted.