Knock it down with a file then work them on a belt sander until the tops of the beams are smooth. Removes stress risers so cracks have no place to form.
All grinding should be done in the CORRECT direction--parallel to the length of the rod, as in draw an imaginery line between the piston and the crank and all filing, grinding, sanding, etc. should be done along this line.
It is also a very good idea to have the rod's surface shot peened for stress relief-not many shops can do this they shot peen for cleaning only, not the same and a huge difference.
Then heat in an oven for one hour at 400 degrees and you've done all you can--unless you want to send them out to be cryo'ed. http://www.metal-wear.com/
In which case all the heat- and cold-treatments will be done for you
Of course, it is wise to have the rods manafluxed for cracks before anything is done.
As Clay said..... remove the large casting flash with a file and then polish in the direction of the rod. You want to polish always in the same direction. This is what my machine shop also told me.
Won't a DA sander polish in an orbital rotation? A Dremel would suit you better and a coarse file initially. This is what I did to my rods...... and had the whole shebang rebalanced and ARP 2000 rod bolts added.