Hi everyone!! I'm renovating the basement, have chipped out the floor & laid insulation, underfloor heating, new concrete!

I've chipped into the walls for electrical & sockets, these have been roughly patched with repair mortar!
The walls are insulated on the outside with isodrän, on the inside I think it's lime plaster & painted!
Now I'm wondering what I can plaster the walls with to get a good surface (planning to plaster all walls in a thin layer) do I need to scrape off all the paint+plaster before plastering :-?
I'm going to paint with paint & something you mix in to get a textured surface (not sure what it's called) ;D
Best regards Vasse