Painting - Taking of Shine

I am going to refinish a family room which was originally decorated about 18 years ago. The finish on the crown molding, wainscoat, and toe molding are stain, varnished (or possibly finished with polyuerthane) and probably waxed. I plan on painting these now, and know that I will need to take the shine of by either sanding or using a chemical sanding agent, and then apply a coat of Zanser 123 before painting. My question concerns the liquid sander which I have seen at Lowes and HD. Is that a good option to manually sanding, and is a primer such as Zanser still required? Is it as messy as sanding - which is a serious concern for me since the room is carpeted? I will appreciate any help and suggestions. I have received some very helpful suggestions and information to other questions on other of my projects, and I am very grateful for your taking you valuable time to help me resolve my questions and problems. Thank you very much.

I believe that you could scrub this trim with mineral spirits and remove all of any wax. It would also remove any dirt and grime. Zinsser 123's label says that application over gloss surfaces is appropriate; and I suspect it will do well.

The purpose of sanding is to degloss the surface of the finish. Zinsser 123 is an agressive primer that seems to bond to almost anything, in my experience.

Wiping on a chemical deglossing agent as you prime might be reassuring. I would not skip the primer.

A good, tarpaulin drop cloth might be a wise investment for working in a room with carpet. I have found it to be.

Hope this helps.