Best Way To Get Refund

I’m a homeowner in CA and recently got some work done to my bathroom. Turns out there was a leak under the shower pan that was causing wood rot. Long story short, I paid a contractor over $8,000 to fix the flooring, shower pan and tiling. It took him 4 months to finish as he would come occasionally and, when he did come, it was for 2 hours of work. After this nightmare of a drawn out process and not being able to shower for months, it turns out that most of the work was done very poorly as a second and third contractor verified. Since then I’ve had to hire a new contractor to fix the old work.

But what I want to know is: what’s the best way to get a refund from the original guy? He’s a licensed contractor in California. Should I file a complaint to the State Licensing Board or just take him to small claims court?

Thanks in advance for all the advice! LMK if you need more details.