I would not just hand the piece to an industrial sandblaster who is not a gunsmith.
If you want to do it yourself,Harbor Freight has a sandblaster that looks like a touch up spray paint gun with a top reservoir for about $15.They also sell zirconia sand.Glass beads are another option.I would not use play sand,it has big rocks.
I don't know your skill level.A blaster will round corners,mess up screws,the crown of the muzzle,etc.
If your freindly local gunsmith doesn't have a sandblaster,maybe bring him the $15 one.
Here is how I look at it.With the competition of the big box stores,the small shop can use the business.If there is someone who can do the job well for you,let your gunsmith make a few bucks.The big box store will take your money and sell you things a bit cheaper,but they won't be there for you when you need them.If you want to have a local smith,support him.