Bad vendor experience has upset the customer, what to do?

Hi all,

My business has to do with "custom car culture" I do custom painting on cars, trucks, and motorcycles, mostly pinstripes and hand painted door art. I airbrush as well. The airbrushing is more complex and technical using general auto body techniques (base coat paint, art with base coat paint, then clear coat to protect and make shiny).

Small stuff I can do in house but for whole vehicle I'll "partner" with someone that has a spray booth or garage to do the prep, base, clear, bury, and buff and I'll do the artwork in between. Of late lots of patina cars with pretty shiny candy and flake "patterned" roofs as that's trending.

I tried a "new guy" who had decent work from other projects I had seen him complete but long story short the project he did with me did not reflect that. I had to have it fixed by someone else and they inform me the "new guy" incorrectly prepped the roof. It will have to be done completely over unless the customer is willing to live with the three nickel sized bubbles in the top center. (*Update he isn't and is livid*)

Should I go after "new guy" and demand a refund? He was paid separately although I recommended him for the job, or is this my responsibility and I should come up with the refund? The customer for the most part was happy with the airbrush work but now feels I have mismanaged the whole deal and doesn't even want to see me. Help!