I've used shellac for things that won't get a lot of wear (mostly for the practice in applying shellac) and waterbased Poly (Polycrylic) on things like table extensions, sleds and other jigs that will be seeing more wear.
I have sleds I have been using for years. All surfaces shellac and wax . . . still going. Shellac is quick to dry, inexpensive and easy to repair although I have yet to re-coat any of my jigs.
Smaller jigs or "first draft" versions will some times get treated with whatever I happen to have been using (usually shellac or some type of oil). My "temporary" outfeed table (3 years and counting) has a particle board top that catches any clear finish I happen to be using.