Bunnings are correct but the level of finish and the lenght of time you need it to last is different to what they are thinking.
Problem with paint is that it moves in a different time frame to what glass moves and as the paint cant stick long term to glass, it slowly breaks down through movement.
Spray cans will do the job near enough.
Splash backs behind oven are an example of straight paint being useless for the expansion retraction movement and to give you an idea, the meadium for allowing the paint to stick long term costs about $5000 per letre... not very much is used of course. As a back ground, Vynal is probably the best