The acetone will not hurt medal medallions, but there were some that were plastic and you need to make sure you have the metal ones. Removing and replacing them is a real PIA if your grips have medallions with the metal "washers", you'll be best served by leaving them alone.
Just be real careful when sanding the grip, the nickle plate is thin and it doesn't take much contact with sandpaper to expose the brass base metal on the raised surface of the letters... brass letters on a nickel background is another tell tale sign of a bubba'ed refinish job.
Also when refinishing checkered grips, it's critical to not to over apply any kind of finish to the checkered area... otherwise it will scream "bubba refinished me" when too much is applied and it partially fills in the checkering.
I like Tru-oil, and when I apply it to the checkered area, I use a diluted solution of Tru-Oil and mineral spirits that's like water, and I dip a tooth brush in it, wiping the excess off it with a cloth and then I brush the checkering. Let it dry and then put a second coat, that's about all you need.
When staining, I do the same thing as it well. I thin it down and lightly apply it with a tooth brush and I use another dry one to soak up any excess. Checkering acts like end grain and will suck in more stain than the surrounding wood, so you want to apply it sparingly and a thinned mixture gives you more control over it.
An alternative to staining is using a tinted oil varnish, which is actually what most commercial production line applications use. They don't have the time to dork around with putting on a stain, letting it dry/setup and then apply a top coat.
A lightly tinted varnish helps to even out minor irregularities in the color of the wood without covering up the grain, and is a one stop process, I believe that is how S&W originally did their grips before going to a sprayed polyurethane.
Hope this helps.
