i know it is already present, but i wanted to change the paint kit for airports in other (non-UAE) Bahrain, for example 
That's exactly what I've said: if you want to just add Emirates to an airport that doesn't have them already, you DO NOT repaint anything. You just change the couatl.icaoprefixes parameter in each sim.cfg for every vehicle, in the [flitsim.xx] section that calls models with a _EK name.
Since by default the couatl.icaoprefixes is set to O ( letter "O" ), Emirates will appear in every airport with an ICAO code starting with O. Of course, as explained in the PaintKit documentation, it's a *scoring* system so, if there's another operator has a better score, perhaps because they have their code in the atc_parking_codes of the parking in the scenery AFCAD but Emirates doesn't, that operator will always take precedence. Or, in case of a tie, the selection will be random.