I just thought of another one, I better get I down before I forget it!

If your client is thinking about "fresco" because they like the antique, Pompeii, type look - then real fresco is the only way to go. You can utilize the fact there are multiple coats for antiquing by chipping away the top layers to reveal underlayers. Don't forget you can tint or color the layers - there is a whole other art form called Sgraffito, scratched plaster or white cement, which uses this technique to beautiful effect for interior and exterior applications. With practice, you can also initiate cracks. These cracks, sputters, chips, tool marks and pops (all plaster defects!) can never be properly reproduced in acrylic. The surface can also be wet sanded after curing, to further simulate natural wear. Again, this is a practice thing, and a learning curve I am on myself - don't expect a video anytime soon! Study the antique frescos and figure it out.