clipped

Mildew growth on your bathroom painted walls and ceilings is NOT usually
a water problem. It's a paint problem. If you use a paint made
specifically for use in bathrooms, it will have a powdered mildewcide
added to it which gradually leeches out of the paint film fast enough to
kill any mildew spores that land on the paint but slow enough to keep
the paint mildew-free for a long time. Zinssers guarantees their
PermaWhite Bathroom paint will keep your painted bathroom walls free of
mildew for 5 years, but if it only lasts that long, you got a defective
can of paint, or you shot yourself in the foot by putting on only a
single coat. If I've taken the trouble to mask off my tiling, my door
frame, my toilet paper dispenser and my light fixture, then I'm gonna
put 3 or 4 coats of bathroom paint on to ensure I have a HUGE reservoir
of mildewcide on that wall which will gradually leech out, giving me 15
to 20 years of mildew free; not just 5. After all, once all the masking
tape is on, how much work is it to put on another coat or three if you
do all your corners with a 3 inch roller and the walls and ceilings in
that tiny room with a 10 inch roller. Hint: Getting the bathroom ready
for the first coat takes a full day of removing towel rods and taping
off what you can't remove from the walls and ceilings. Putting on the
1st, 2nd, 3rd and 4th coats and removing all that masking tape can be
done the following day.

I've never used "bathroom" paint, only alkyd semi for
baths/kitchens/doors/trim. We had a very mildewy shower stall until we
put a timer on the exhaust fan. Previously, it operated on/off, and if
we left it on, we would forget to go back to turn it off. At the same
time, we had some pin-hole defects in the 35 y/o grout (neighbors in our
condo, all with same tile jobs, had major wall damage due to
deteriorated grout) so I regrouted the 1x2" grout. Don't remember what
sealer I used. Made a point to leave the shower curtain open on both
ends, and spread out loosely, which allows better ventilation.

I'm not arguing with your method, but my logic tells me that mildew is
far less likely to grow on a smooth, dry surface. Alkyd is pretty
impermeable, so a bleach wash/rinse prior to painting is good insurance
to not paint OVER mildew.....it is the universal method of painting
exteriors in Florida where mildew grows in about 5 min. without direct
sunlight.

Four coats? If two don't do the job, two more won't help at all.

"Man made marble" is called "Corian" if it's made by DuPont, and other
trade names depending on who made the stuff. It's actually a thick slab
of Plexiglas to which natural clays have been added during manufacture
to give it a "marbled" appearance. So, man made marble is really just
adulterated Plexiglas. Never use nail polish remover at a Corian
bathroom counter top. That's because nail polish remover is acetone,
and Plexiglas is polymethyl methacrylate. Acetone dissolves polymethyl
methacrylate. The good thing is that polymethyl methacrylate is a soft
enough plastic that you can polish damage out of it much more easily
than you could with a granite counter top.