If it's a machine I'll use, as opposed to one sitting all purty in a collection, I use a high-grade furniture wax instead of shellac or poly. The wax gives it the beautiful finish you want, but it won't show the scratches from pins, etc like it will on shellac or poly. Here's a photo of a 15-91 I restored last month.
I only restored the top, I left the sides alone. I used denatured alcohol to dissolve the old shellac and once it was dissolved I spread it thinly and let dry. And then I used Briwax in the Mahogany tinted version, and voila! It's beautiful again.
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