What legal process or issues to do a AR sale private to private from CAL to AZ? From what I understand AZ does not require any FFL transfer for it. Is this true, and if I do - is there something I need to do in Cal?

Since it's interstate, it has to go to an FFL in AZ - can't go direct to the buyer.

Since YOU'RE in California, you're technically required to go through a California licensed "AW" dealer, unless you personally transport the gun across the border to the buyer's AZ FFL.  California usually doesn't care, however, as long as you're moving your illegal baby-murdering "assault weapon" out of their pristine (and now, bankrupt) state.

If you properly registered it as a Cali AW before 12/2001, you're supposed to notify DOJ that you've disposed of the weapon.

Circuits pretty much has it.