Trade/Registration and protection of a film company name.

Obviously, you should hire a lawyer to help you with this and your other business formation and IP asset issues. Besides the TM application(s) (and domain name registration, and entity business name, if you and your DP are partners or supposed to share ownership, do you have a partnership agreement or LLC operating agreement, so you have down in writing who would owns these assets and what happens if one of you wants out?

It's pennywise and poundfoolish to leave a lawyer out of the legal process. Just look at the AVvo questions from people who wait to contact a lawyer until AFTER they've signed something or not signed anything at all.
Plan for success by making sure you get good advice before you commit TM infringement and have to start from scratch after investing time and money on a name that's not available and likely to get you sued.

Disclaimer: Please note that this answer does not constitute legal advice, and should not be relied on, since each state has different laws, each situation is fact specific, and it is impossible to evaluate a legal problem without a comprehensive consultation and review of all the facts and documents at issue. This answer does not create an attorney-client relationship.

Would you go see a film that was made by an attorney who was moonlighting as a filmmaker? People specialize into careers for a reason, it provides significant efficiencies. The USPTO makes it very easy to apply for trademark registrations, but that doesn't mean that it is a good idea to do it on your own if you are not familiar with the process. The simplicity of the web-based system provided by the USPTO masks many complexities and pitfalls. IP attorneys file trademark registration applications all the time and often offer relatively low fees for the service. Hiring an attorney for this work will allow you to focus on filmmaking rather than the intricacies of trademark law.