Answers:
Work away from the light ( start at the window )
work your roller in the same direction face on with the window.
over lap you paint strokes by at least 30%.
ceilings dry quick, if your paint is thick just water it down by 10%, this will ensure your dry time to take longer so the ceiling dries as one.
dont use any vinyl based paints.
if your in kitchen or bathroom use eggshell.
prep the surfaces well.
remember, the decoration is the fastest non time consuming part of the job. put every effort into getting that surface as perfect as you possibly can.
Easi fill is used for the plaster board tape and join method.easi fill is ideal for decorating, either small or large areas. the integrity of the product is not affected when used either thick or thin. use a vinyl based paint as your first coat, this ensures the easi fil will not flash through.
I'm afraid you cant. the properties of the undercoat are not made to withstand the weather it is set to endure without its top coat. get the colour scanned at your diy store and have it made into a top coa finish. try an eggshell as your finish coat. this is similar to the flat look with almost no shine finish that you like in the undercoat.
The paint could well be of a distemper finish. use a water based stain block. one good coat should do it.
No number of coats of more paint will sort the issue. not even a hundred.
you need to clean the area, spray bleach if mouldy. let it dry, sand if needed( prep is king ) .apply a coat of zinsser stain block. water or oil to suit your finish.
now once dry, get your desired finish coats on. job done