Make sure the walls are gooey. If you don't then the paint just sits in the surface and is easily knocked off. Use a broom to apply. Rollers are no good. Brushes are too slow.
First coat ends up a mixture of mud and paint.
Allow for at least 5 coats. If you want clean lintals and top plates, mask. Slightly more geletin seems to give a better result. After every coat mist the surface for a couple of days. This alows the paint to set without cracking.