That's interesting. I'm trying to figure out why he has you approve his work and what the sign off relieves him of. I think it's a nice gesture that he had you come over and look at it, but here's the thing I don't get.
He's a pro and he ask you, a novice, to approve his work.
What are you suppose to do, look at it and tell him it's okay to shoot with paint.
If it was my truck I'd want to see it before the primer was put on to see the prep work that all that primer has covered up.
Primer covers a lot of things which even an expert eye can't see.
Being a painter I am amazed sometimes when what I see looking good in primer turns out to be not what I thought because primer does not let you see it but the glossy top coat does.
It's hard for me to say a lot, because I know nothing about the condition of your truck and the body work it had to have prior to the prime he asked you to look at.
What does the sign off mean ? Have you spelled out to him what you expect the final product to look like, because if you haven't told him in detail, his idea and your idea of the final product might not be the same.
Here's another thought to consider. When you pick that truck up when he's finished, after you've looked it over, payed for it and bring it home is when your going to start seeing all the flaws that he left in his work.
It is really hard to find the flaws unless you inspect every square foot of that truck, but you'll find them, when you wash or wax it later.
When I painted for someone I sure didn't need their approval during the stages of my work, because I knew the quality of the product I was going to turn out which depends on what the customer expects and is paying me for.
I really question this sign off thing. After the work is completed and you find something you don't like is he going to say,... You approved it, what can I say, sorry bout that.
As a painter I will say it is hard to deliver a product that meets a customers expectations and stay within the quoted price.
If it was a T&M job, I could deliver what ever they wanted, but that means they had to pay for what they wanted, but they still got more than they payed for because I took pride in my work.
Dan