Having been a professional Artist for 36 years , I've painted practically everything , and seen their conditions as they age .... I'm all for the new water based paints , latex, whatever... The oil paints were fine in their time , but the new paints (if you buy good paint ) perform even better ...I've done outdoor murals in latex that lasted about 10 years before drying out (oils only went 5Y in similar cond.)...in constant sunlight ... as Micro did , my house @6years looks like new... It's good stuff , and I definitely would NOT put it over oil base , or oil base over it .... sooner or later it's gonna' come off .... ask me how I know !!!!
Thing is , you have to be patient .... it takes Latex a week at least to harden , to where you can work it ...
want texture???, spray a light coating of household texture , mixed with a good glue like Tightbond 2 (doesn't take much ) works !!! when the paint is gone the texture will still be there...