Several options are available to you. One thing in common with all of them is your patience and skill at wielding the tools.
A dremel or fordham work well with the Cratex wheels. I have tried them, but find myself without the feel for the tool. I just can't seem to get repeatable results easily from one side of the gun to the next.
A file is a good choice. I like to use the swiss pattern files and a fine cut lathe file. This is my prefered method. I just like the feel and control I have with files. To get the smoothest finish after I file, I use a combination of shop rolls and honing stones for the final finish.
You can even do it with honing stones alone, but it takes quite a bit longer, the results are entirely satisfactory.
I have seen some guns that I suspect were done on a beltsander. Lines didn't look all that good to my eye. Even some of the "name" guns I have seen didn't hold the lines all that well. For some people this is not a big deal, for others like myself, it just doesn't look right.
As in all things, practise with some scrap steel to get a feel for what you like best and can control.
Final surface finish of the steel depends on what your going to finish the gun in. I've used bead blasting, shot blasting, fine sandpaper grits, and diamond polishes. All work well in their propper context.
To dehorn, I use Swiss files, #2 cut, as well as aluminum oxide paper and cloth in 220, 320, and 400 grit. To back the paper, I use wooden dowels, metal and plastic rods, round pens, and block pencil erasers. The erasers are great for staying with the lines while just softening them slightly. I prefer the feel offered by hand tools over using the demon Dremel. Remember: you can always take more off, but you can't put it back on!
i just did my springfield stainless. i used what are called "EDM" stones from a company called "CONGRESS" a machine shop that does EDM work or builds molds could tell you where to get them, or a tool supply store. i dont know if brownells has them but they might.these stones come in different sizes and grades. i was real pleased with my results.
If you decide to farm out your dehorning job, you might consider Robar. A friend of mine has sent several pistols to Robar for just dehorning and refinishing (or just bead-blasting if stainless). They came back nicely done. http://www.robarguns.com