I would just use shellac since that's the last coat, but I really like shellac...

I know that wasn't the exact question

 

Shellac is actually the only finish I use at work. My boss is very old school . I find it to be very time consuming with a lot of room for errors. And what I’m really worried about is that it’s not a good finish for bathrooms

 

You could do that but the Rubio is not really made for that purpose. It would almost be like putting Johnson paste wax over the shellac and call it a finish. It's designed to be applied to raw wood. If you were to use any other finish the shellac may be an issue because of the natural wax contained in the finish. You would need to seal it with a de-waxed shellac such as Zinsser Sealcoat first. About the only finish that will adhere to standard shellac is lacquer and old fashion varnish. When polyurethane became popular painters were having problems with it not adhering to shellac so Sealcoat was developed. In the 1950's knotty pine was popular and painters would paint the knots with shellac to seal in the sap and then varnish over it.

 

A quick wipe with naptha will remove any wax residue. I use shellac on most projects. I have never had adhesion issues. There is never a problem with shellac over shellac.

Quick tip...if you ever want dewaxed shellac from a can of zinser blonde, open it without stirring and the stuff on top has no wax.

 

I believe Rubio Monocoat needs to go on raw wood so it can be absorbed into the grain. Wood sealed with epoxy will prevent the finish from “getting in”

 

I believe if you use dewaxed shellac and you can top coat with anything. The flakes last a long time so just mix up what you need. A wide range of colors are available. The stores near me have raised the prices considerably.
https://woodfinishingenterprises.com/page/4/?s=Shellac Wood Finishing Enterprises seems to have decent pricing but I have never made a purchase from them.