Heres the facts on shotgun barrel modifications:
1. Porting will greatly reduce muzzle jump and what the shooter feels on his or her face. Some porting patterns seem to work better than others. My personal favorite is Angle Porting.
2. Lengthened forcing cones will give you the most value for the dollar in reducing felt recoil. Backboring a barrel does not have a marked benefit on recoil.
If you want to make a gun feel the best it can...get it ported and lengthen the forcing cones.
As far as "burning" the porting into the barrels. What most places do now, including Angle Porting, is use Electrical Discharge Machining which leaves no burrs on the inside of the barrel like drilling does.
Oh yah, I know all this because I used to ba a master class sporting clays shooter and fired 30,000 twelve gauge shells a year. So I have a lot of experience in what shotguns kick like!