You can get it quick, cheap, or good -- any two out of three (not perfect, but there are few options for a high quality finish that will be quick and durable and last). Skill and practice makes the good come much easier. That is especially with plastic finishes such a CA or plexiglass -- practice and skill makes a difference in the ease and quality.
Sanding sealer is the finish with additives that lubricate the sand paper. Commonly these additives are stearates. They make the sanding easier, but make the finish weaker, and adhesion between layers a bit harder to achieve. That sticking of layers is less important with lacquer than with varnishes.
Open grained woods need to have the grain "holes" filled, and the high spots brought down. Known as "leveling" in the finishing literature. Note that you will likely need the abrasives supported firmly (not by fingers) to successfully "level" evenly. You are headed towards filling with many layers of lacquer -- and that is not quick last time I did it. Lacquer also needs time to "cure" and set hard. The result is a good hard finish that polishes well, feels good, and wears a long time.
Quick and good --- not in my experience.