From a tactical standpoint what do PSYOP do and how often do they work with 3 letter agencies such as CIA or FBI?

Regardless of level, tactical or otherwise, as a PSYOP professional you are expected to interface with members of the interagency.

As the MAJ mentioned, you can get the most detail from the SORB. But in a general sense, there are two main areas that you will work in. You would be assigned to a Tactical PSYOP Unit or a Regional PSYOP Unit. The tactical units have the Tactical PSYOP Teams (formerly callrd Loudspeaker Teams). There are the small teams that work directly work with infantry units or other units in direct contact with the population. They practice "face to face" PSYOP, employing their cross cultural communications and language schools to directly influence the people. They may create some PSYOP products themselves or disseminate products produced by the PSYOP Task Force Regional Units.

The PSYOPers in the Regional Units mostly work in Product Development Centers creating PSYOP products such as radio broadcasts, TV and other video products, or printed products such as leaflets, newspapers or posters. These may be products that are disseminated nationwide using US or local assets, or they may provided down to the Tactical PSYOP Teams for their use.

So that's a real broad breakdown. You will either be creating PSYOP products or disseminating them. You could be working and living with an infantry unit, or you could be located with a Task Force HQ , or even creating products at Ft Bragg that are transmitted into theater electronically.

Note: after I typed this I remembered that they changed the name to MISO, so you might need to replace my PSYOPs with MISOs, but the idea is the same.

Whenever you have a change stop by the Recruiters at the Military Information Support Operations Recruiting Detachment, Special Operations Recruiting Battalion at Fort Bragg. You will get the right answers to all of your questions.