If you are in Long Beach area, I know two really good painters there with really long lists of references and boats at the local marinas where you can see their work going back 10+ years.
Elid Cordon -- (323) 252-3799
Hector (Forgot his last name) -- (323) 571-1775
They work dockside and have done tons of boats from the waterline up. Hector has been working on boats on the docks there for at least a decade, maybe more, and Elid claims to have been painting boats in the area for 40+ years and no one doubts him -- he's been around as long as the oldest folks around can remember.
Hector usually works by himself. Elid sometimes works by himself and sometimes brings a helper or two for large jobs. They both do deck core work. They both primarily do Awlgrip. I think I've seen Hector do some boats with Kiwigrip for the decks. Not sure if Elid uses it ever, or just Awlgrip.
Hector repaired my mid deck core and painted all of my decks and refinished my transom, as well as refinished one of my shower enclosures and built-in fiberglass lavatory units. He also cut out two live wells a prior own had built into my aft deck and refinished it and the back of the aft cabin on the outside, where the built ins had been built in. He used Awlgrip for everything. The work was flawless.
When I went to paint my whole boat, I switched to Elid Cordon because he happened to be able to schedule it sooner and planned 50% less calendar time because he worked with a helper.
My boat was very deeply crazed, so it wasn't an easy one to paint, either. It had to get sanded down to the glass, built up with layers of primer, and then painted. The transformation was amazing. I got quotes $80k by local boat yards, $40k by the yard in Mexico, and Elid was $15k. He recently did a 42' Grand Banks, waterline up, for about $25k there.
When it comes to replacing core, I've seen Elid take on bigger jobs than Hector. It might just be what I've seen, but I think it also might be that Hector might avoid recoring jobs beyond a certain size because he is only one person. I don't know.
The prices they quote are about the same. I think they know each other and often communicate to keep it that way and not undercut each other.
Hector's work is 100% flawless. Elid's work is nearly as good, but I did occasionally see something I thought needed revision -- and he always did it without complaint or any push back. He normally blamed his helper and apologized. As a for example, there was a drip mark on my transom, so he sanded it and repainted the whole transom without complaint.
No one I know has ever known Hector to try to renegotiate a price once he gets into a job. Small renegotiations with Elid seem to be the norm. He might come back and say that he didn't know X was supposed to be included, or Y needed extra prep. But it is generally such as small amount that no one wrestles much with him over it. None of these things have every resulted in anyone being unhappy in the end, more like gentle head shaking, "You thought I wanted all of the brightwork done -- but the ladder?"
I used to keep my boat at Island Yacht Anchorage #2 and they both have worked on tons of boats there and at #1, so you can walk the docks, see their work, and talk to dock neighbors. Some people get transient slips there to let them work on boats. Usually the marina manger puts those boats on the far side of #2, and the A dock to keep the work away from other boats. They both seem to do work at certain yards between there and Marina Del Rey. But, I think Elid spends most of his time working at the Island Yacht Anchorage marinas. They are both well known the the management there, and keep it clean enough to stay in their good graces and keep the port police and uscg happy.
At any rate, I can't say enough good things about either of them. As a brand new boater with a project boat and "fool" written across my forehead, I was losing control of project after project, having to have things redone because I didn't know enough to get them done right, etc, and these two folks dealt me a fair deal, followed through, and did work that passed the test of time. I saw my old boat a few months ago, and it still shined like new. They took care of my friends and dock neighbors, absentee boat owners, etc, and there was never a problem.
Elid Cordon -- (323) 252-3799
Hector (Forgot his last name) -- (323) 571-1775