I've done it both ways depending on the blade and the complexity of the filework. After a blade is hardened I often have to rough in the design with a dremel rotary tool and then finish it with files and sandpaper.
First, like your handle man. I shoot left wing fletching myself. LOL
Next, lets get this out of the way. I'm no expert. Do very little of this kind of thing. I will say, if you are like me and do home heat treat and don't have a VERY GOOD oven, and protect the blade with clay or packets, wait till after it's heat treated to do the file work. The large amount of scale produced by quick quench methods will likely destroy much of the detail you worked so hard to put in.
Then you can do as Mike says and use diamond bits on a drimel to do the bulk of the work. Which works great. Or....you can even do a deferential quench that leaves the spine and tang a little softer to work. Or even soften them after heat treat if you know how. Then do the file work. I've done all three.
If you are sending it off to be treated in an atmospheric controlled oven, clean up should be as simple as sandpaper in most cases. Basically just redoing the last step before you sent it off to redefine the detail.