I just moved into an 80-yr-old apartment which has clearly been the victim of "good enough" fixes for at least 60 of those years. Worst is the painted woodwork (doors, frames, baseboards, etc) where people have slapped successive layers of gloss on top of paint that is peeling, cracking, or has drips, without any attempt to fix the problem. The result is a mess that needs deep sanding, and some filling, before priming and painting. However, several layers down is lead-based paint. (I did one door and was - rightly! - severely lectured by my doctor. Luckily I don't have kids or pets).
What I would like to know is: Is there some preparation that I can use to create a smooth surface on top of what is currently there, with only a light surface sanding of the existing paintwork to make it stick?