Your message is confusing to me. You start by describing a clear finish and end by describing a painted finish. If you plan to paint the piece, there is no need for French Polish or Shellac.
Shellac is used as a sealer in many cases, but paint is a sealer unless you have something you are concerned with color bleed-through. Color (especially darker colors) can lift and bleed through a light colored paint over time. This could be from old stains, inks, magic markers etc. A primer coat of Kilz will seal prior to your final paint color and prevent bleed-through.
If you don't have time to do it right the first time, when will you have time to do it over?