We always tried to move things out of reach, I don't think you can blame a 19 month old for touchinh something interesting if we've left it out.
We kept our no touching things for things we couldn't really move like the DVD player, tv, that sort thing, last thing you want to be doing is saying no touching all the time cause they will then just not take any notice. So try pick your battles.

Discipline wise at that age I used to remove her from whatever she was doing and use distraction methods, like we don't play with the tv lets play with this instead, if she kept going back to it then I would move her into a whole other room which she hated and would stop doing it.