When using latex be sure that the temperature is above 50 degrees F. It is difficult for latex to form a film at lower temperatures. With solvent-borne paint, be sure the temperature is at least 5 degrees above the dew point. If it isn't, water may condense on the surface as it cools while the solvent evaporates, causing an uneven blushing effect.
A small mirror of the kind carried in purses can be helpful in diagnosing toilet clog problems. If the toilet becomes clogged, position the mirror so it reflects up the drainway. Then shine a flashlight on the mirror to see if a foreign object like a child’s toy is causing the problem.