i have used MEK successfully for years on poly type finishes....use it outside, take a small metal pan and a cheap chip brush and simply brush it on the finish. it will dissolve any finish i have ever encountered (including the doublebased stuff that browning used to use)- and because of it's high volatility will leave the wood as dry as an ancient piece of driftwood.
most sherwin-williams stores keep it in stock in both gallons and fives - bought a fresh gallon last year for $37.99....nowadays, it's the only stripper that i bother to keep around.
best regards,
tom
