I have a table type belt sander/disc sander with abrasives for aluminum... so that's what I'd use to get it down to about 85%-90%, then get it to a 95%-98% "shaped" finish with files followed by various grades of wet and dry to a nice 600 or better finish before media blasting. Use a sanding block so your lines and flats stay straight.
Don't think that fine media blasting will make scratches disappear... unless they are 400 grit or finer scratches, that's not going to happen.
You can do it with nothing but files, but it will take a while. Look at it this way... if you've not filed much aluminum, this will be a good way to learn what works and what don't.
Get a file card to keep your files clean. Use good files like Heller and Nicolson for examples... and if you can find them, aluminum files. Load your file with chalk or soapstone before filing... keeps it from clogging up too fast.
Here's an interesting quote from the Aircraft Mechanic's Pocket Manual:
"As the file teeth point forward, the file only cuts on the forward stroke. On the return stroke the file should be raised slightly to prevent dulling the teeth. Note: In filing soft material such as aluminum, Dural, lead, etc. the file should be drawn back over the metal as the teeth are cleaned on this stroke."
Take your time, have a plan, don't try to do it all at once, stop when you get tired... and have fun!
C
