Jan you can buy lacquer in a can for brushing but you don't want to try it because is will leave brush marks spraying is the best. Nail polish remover is acetone but contains some kind of oil so it is easy on the hands. Acetone will try out you skin in a hurry. You can try it but it will take longer to penetrate the finish because of the oil in it. Make sure sure you are sanding with wet and dry paper with a lubricant so the finish will take a very smooth coat of paint if needed. If it turns out to be lacquer you will need acetone anyway.
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Ps if the alcohol softens the finish no need to check with the acetone test.