In article ,
Ian Stirling writes:

Are you using a quality brush, not one out of the 99p bin?
IMO, painting tile looks horrible, and I'd always retile.
But that's me.

My brother painted some tiles white with what claimed to be
special tile paint but looked just like over-priced gloss
paint. A year later it was all yellow, and he had the tiles
all taken down.

--
Andrew Gabriel