I've had moderate success with mindfullness yoga and zen meditation in the past. The meditation sessions can get intense as you essentially have to imagine any negative thoughts and emotions that enter your mind, and try and sit with them, until they dissipate. I was using creative visualization as an adjunct to create the internal image of a 'thought chamber' where I could observe painful memories and the attached emotions while feeling detached slightly by the thought of some kind of thick glass barrier separating me from the incoming slew of negative ruminations. I didn't keep it up because my flashbacks still eventually get me rattled enough to stop meditating daily.
I used to get upticks of spiritual inspiration where I could sit with my trauma a bit and let it pass...I've lost the patience nowadays though
Other things that are less healthy that I've tried that worked was Kratom, occasional usage of benzos, and propranolol. The latter doesn't stop the mental ruminations, but it blocks most of the flight-fight-freeze response involved in PTSD. It trains the mind that when flashbacks occur, there not really life threatening situations, because the physical component isn't tied to the traumatic memories and ruminations anymore. I still feel anxious mentally and even wonder sometimes if the beta blocker is just tricking me to believe I'm safe, but it stops me from entering into a full episode where I lose time and act out of character responding to stimuli that isn't even threatening in reality
...If you suffer PTSD you know what I mean. All your senses seem to meld together and your surroundings seem to exist in an altered state of perception, usually of a hellish nature. Then the world starts spinning wildly as people who you were having a conversation or listening to moments earlier become enemies who suddenly possess sinister intentions. Then the need to get my head back to a less scrambled state and quarantine myself for everyone's safety becomes urgent.