I love shellac for (1), the fast dry and repair ability and (2), the color and depth as an alternative to slow drying oils.
Never tried IPA, though the best stuff I can find is 91% and I've read that a lot of the less pure mixes have glycerin mixed in.
Always thought DNA was just tainted alcohol, never thought about the methanol and other stuff added.
For sealing, due to the high price for buttons/flakes, I use the Zinsser but it has an odd odor that says it is not a typical solvent used.
The colors produced with amber shellac and air dried walnut is one of my favorite combos.