Three referrals should be enough to assess the quality of work as well as the communication skills of the painter. Ask about the overall quality of the work, the work style of the painter, how the work has held up over time, and if they would hire him or her again. Be wary of any professional that refuses to give you references; a quality painter should be happy to have to speak to past clients.
My husband has been a professional painter over 30 years. He prides himself in his high level of work ethic and customer satisfaction. He stays up to date on techniques and finishes. He gives Very detail and accurate appraisals with contracts. At an alarming rate, as he starts to finish the last day or the day before, the client starts nit picking and being disrespectful towards his work when every day prior to that, they were very pleased, as he request ongoing satisfaction throughout the job. Then they don't to want pay remaining balance, bicker about final cost, or stop payment. He has a crew he has to pay whether the customer does or doesn't honor the contract as well as our own household expenses. Wasted time ,labor, money and effort lost. Now how do we fix this? Remind yourself and clients that a contract is based on honor.