I am lucky enough to have a bathroom with a door inside my bedroom that also has a door, both with locks. but for people who may not have a window / fan, try doing this and you will not get caught. ive been doing this for 2 years now and have yet to be accused of smoking.
1) bring with you to the bathroom a lighter, sploof, and a pre-packed bowl if possible (if not just pack it while sitting on toilet)
2) adjust water to as hot as you can stand it. challenge yourself to shower in pretty hot water because the more steam there is, the more the smelly smoke will be absorbed
3) literally stand in shower for a few minutes; relax and let steam build up
4) take 1st hit facing away from shower (water hitting back of shoulders) so your valuables dont get wet
5) hold breath for as long as possible and hold sploof over the bowl so the smoke that floats around after your hit rises straight up through the sploof
5) blow smoke through a sploof aiming anywhere in the shower but downward, because we all know heat rises, and if you can see it, a lot of steam will gather near ceiling anyway
6) keep hitting your bowl throughout the shower, and finish it about 5 min before youre done; dont vacuum your bowl so its gone in 30 seconds, and dont wait till you step out to take 2nd hit.
[in between hits, i recommend setting everything down on the back of the toilet on toilet paper, or a towel so nobody hears the glass on glass clanking]
> remember to use extra soap
if you think someone knows your blocking the door with a towel, just say it was the clothes you took off
when youre drying off, ash your bowl into the toilet (or flush cig butt) and put on deodorant immediately. if you have to walk to your bedroom, wrap your stuff up in your clothes.
hope this helped