Would Pledge Furniture Polish (Citrus) be a good substitute for guitar polish and cleaner? If not, what would a good substitute be?
i use lemon pledge and it works just fine
"you have a short attention span...

NO were not."-metalocalypse
Pledge (and most polishes) leaves a silicon residue that is almost impossible to remove. Should you ever need to spot-repair pain chips or glue something, the paint/lacquer/glue won't stick.

You can use it, but I'd look for something silicon-free. Not a big deal for electrics, but a huge deal for acoustics.
unless your about 100 miles from a guitar shop, guitar polish isn't that expensive and lasts quite a while

but if you must any good wood polish should do
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