I've ported several handgun barrels over the years with varying degrees of success. The technique I've used has been to shove an oval egg sinker down the barrel, further down than where I intend to drill for porting. Then, I heated the muzzle end of the barrel with a propane torch to pre-heat it (like pre-heating a bullet mold), then poured in molten wheel-weight alloy on top of the egg sinker to fill the remainder of the length of the bore with lead. Once cool, I used Dykem fluid to lay out my lines for drilling the barrel, a set of wing dividers to evenly space the holes and a very sharp center punch to mark and index those places to drill.
I then employed a brand new cobalt drill bit in each case, and very slowly, using a drill press and a drill press vice (don't hand hold the gun.... not ever!) I drilled the holes in the barrel. The lead in the barrel GREATLY reduced the amount of burr on the inside of the barrel using this technique. Once the holes were drilled, I drove the slug out the breach end of the barrel, then fire-lapped the bore once again to smooth up the porting job. (by the way, the barrel should be fire-lapped first to remove any barrel constriction at the forcing cone end of the revolver, or you'll play heck getting that solid, bore diameter poured slug out of the barrel!)
Success was varied in each case, with two guns being very well tamed using this technique to port them. It seems that port placement is the key, and I found a 60 degree tapered hole to be superior to a straight-walled hole. It seems the gas escapes quicker, and without a ventouri effect.
However, with the price of guns today, and the very reasonable costs of having a gun properly ported using an EDM, it seems to me, in retrospect to be penny wise and pound foolish to do a shade-tree porting job these days! Sure, you might get a great job, but then again you might botch the barrel.... it only takes one slip, or one hole walking out of alignment when you are starting to drill the holes to really foul up the works.
Just for reference.... I've ported I think seven different big-bore handguns over the years (the last one about eight years ago), and right now I don't own a single one of them... (I think this figure speaks volumes for my satisfaction with the end product!)
However, I've done the same with shotguns, and finished polishing with a brake-hone (used for automotive brake wheel cylinders), and had perfect satisfation.... still own all of the shotguns I've ported!
Weigh the options, then enjoy!
God Bless,
Marshall