I am staining a set of parawood kitchen tables and chairs black with minwax onyx stain. I had to apply two coats of stain and let the second coat dry on the wood without wiping off to get the stain to appear dark and even. How should I seal this?

Can I now apply the minwax polyurethane coating or do I have to shellac it first? I asked Zinnsers about their bullseye shellac and they said that if might give the wood a slightly yellow tint which I would like to avoid. If I directly apply the polyurethane coating will it adhere to the wood OK and seal it?

Any advice would be appreciate.