@cassandra, the fundis will tell you that for plastering you use blue triangle. It leaves a "brighter" finish to which you could use less undercoat paint.

All cement is manufactured to the same standard. From my experience, the brightness of the finish comes from water. Far too many fundis just use any water to do plastering; when standards require that you use water free from impurities. That means the water you use for plastering should be as good as water certified for drinking. But when you use water in which impurities are (ie borehole water), then you end up getting a bad finish, which with time develops line of weakness which grow to cracks. Never ever overlook the quality of water used for plastering. I see fundis getting water from swamps, to go plaster with. wrong wrong wrong!