Can't answer that question personally, as mine was completed when I bought it. The quality of the body and paint is superb after 6000K mi. with no cracking, flaws, or any signs of stress or wear. I don't know how much prep was required. Why don't you just talk to the Weavers, and discuss it with one of their recommended body shops? Unique owners are pretty close and very open, and virtually all I've talked to are ecstatic about their fit, finish, and paint work.
Better yet, why don't you pose your question on the Unique forum:
www.uniquecobra.com
There are a number of people active there, who have recently finished, or almost finished new Uniques, and I'm sure they can better answer your questions. Everything I've read there would indicate that they are very happy with their cars.