Private service processor will cost you more, but can be more efficient. I would suggest service at your ex's place of work or activity when they least expect it. People looking to dodge service are usually on the lookout when they are at their residence.
Best of luck.
Legal disclaimer: The answer provided is for educational purposes only. It does not constitute legal advice or create an attorney-client relationship. You should consult an attorney for legal advice regarding the facts of your specific case and designed to help you with your personal needs.
A private investigator/process server will be able to find the most current information on your spouse using a variety of data bases. In my experience, police agencies will serve process on private individuals, but some of them may not always be that diligent since they have no real interest in serving the person like a private process server. Good luck.
Arthur D. Leritz.
Legal Disclaimer: Mr. Leritz is licensed to practice law in the State of Washington. The response herein does not constitute legal advice nor does it seek to establish an attorney/client relationship, but rather offers educational insight only. Please feel free to visit Mr. Leritz's website for additional information: www.adlergiersch.com