Rob Johnstone explains How to Apply a Natural Finish on Softwoods.
1. Sand the project up through the grits until at least 220-grit
a. It is a good idea to sand pieces that will be hard to reach before assembly.
2. Wipe the project with mineral spirits to check for glue splotches
3. Apply a sealer coat (Zinsser Sealcoat) of a shellac-based finish by wiping: flooding the surface with finish and wiping it off.
4. If you have any nail holes, cracks or defects in the wood, fill them now with a wood filler putty that matches the color of the oiled wood (sand smooth)
5. Apply at least two coats of a wipe-on polyurethane
6. Optional: After the finish has cured for 72 hours, apply a coat of high-quality paste wax and then polish it off.