silk IS emulsion i.e. water based or mixed with water...
bathroom silk is a bit more water resistant, id treat that like gloss...
gloss is oil based and completely knackers the job up, total seal...
silk will suck to an quite some extent..depends on the paint, you can get away with skimming straight on silk, try a trowelfull one night just for an experiment and time it...if it aint solid after 20 mins youll be ok..