Yes, you can use guitar polish on swamp ash and other types of guitar wood.
The guitar polish will remove the surface gloss from the top of your guitars, but is not abrasive enough to strip away the finish. This gives swamp ash electric guitars a “worn in” look and improves tone, depending on how much finish has been removed.
Guitar polish is also a good choice for restoring old instruments to a “like new” condition. They will not change the look of a guitar, as long as you remove all the old finish first. If you don’t mind this, it may give your old guitar the sheen of new wood.
To remove excess polish residue, simply clean your instrument with water. The polish is water based, so this will clear it up quickly. You can also use a wet tissue or cloth to wipe off any excess residue. This is also a good practice for any time you use old polish on a new instrument.
I have used Fender’s polish on the guitar’s finish, as well as several other brands, on guitars of all types. I never had any problems with the finish being affected by polish. It does require that you wipe off any excess from the fretboard and frets, otherwise it will darken them over time