I just was lucky to find a local supplier, in Vancouver, Canada. It is also a 'classified' lime which goes through an air curtain, any granules or small chunks (most likely magnesium) are separated out.

I am evolving towards what I would call 'architectural fresco' . This does not require giornatas or long settime time. This is the making and decoration of domes, cornices,etc., without the 'saints and sinners' but rather by effective decorative motives. The plastering techniques are equally as important as the painting.

You seem to have a sophisticated sense of plaster. The only reason the acrylic is there is to help the plaster stick to a non-fresh plaster surface. Venetian plaster, in its purest form, is a lime plaster which has been pigmented with crushed marble for color. It will take a high polish, just by using the trowel in the final hardening stages. To preserve the polish, in dusty climates, a wax was put on the surface, and you would occasionally wax the walls as you would wax furniture. The pozzolans would result in a much harder plaster, say for hallways, schools, etc.