Yeah, stop fighting it and instead, learn how to let it go. You wrestle with a dirty man and you will get covered in dirt, too (sounds better in yiddish!).
Thank your Sweet, Teyereh Tatty for the memory of the shmutz - and then let it go quietly just as it came to you.
Get used to davening for the people who made the schmutz, for they are sick people who are aniyim b'da'as.
Get used to asking Hashem for an appreciation of the fact that he has helped you now for years not to look at the schmutz - and ask Him to please - it is is His Will - to please
For this to work it needs to be asked with anivus. Leiv nishbar doesn't mean sad, but it means broken - not gayvoh. Asking with gayvoh is like "here I am, You should do this. Nu, why are You not doing this and helping me!?" Not as another selfish child kalbin d'chatzifin and not as a demand.
Humility. Because the only one to blame for the schmutz in the first place is you and me, from looking years ago - and from looking with such intense kavonoh into enjoying it so that it was burned into our memory. Just accept the truth and be humble in front of your only Tatty - you and I are asking Him for what we do not deserve. And He gives anyway, all the time. "...Elokim lo sivzeh."
The pasuk says in Wednesday's shir, "im omarti motoh ragli - chasd'cho Hashem yis'adeini", meaning (OK, maybe it's a drush of mine) "As long as (im - can mean "when" or a t'nai) I say, "I'm going to fall, I do not have the power to do this!", then Your Chesed (Chessed is always even if I don't dereve it) will hold me up and save me". But as long as I say that - don't worry G-d, I got it under control....forget it.
And He will give for you, too. You are one of His beautiful, sweet yeedeleh's (even with the schmutz, kal vechomer when you are not using it)! These memories will leave you eventually. It may take a year or more, but it is better - far better - than adding new memories to them by searching for more schmutz.
Finally, this will only work completely under the condition that you do not still love the memories too much. If you react to this and say the frumeh thing: What? Love them?! I hate them, they are horrible evil I wish I never saw them they are disgusting and terrible and ugly!!" Then I will suggest that maybe you are lying to yourself.
If there is a hano'oh, then part of you still loves - OK, likes - them.
You will not likely be able to change that.
But it is even worse - far worse - to deny the truth. You still enjoy these images when they pop up into your mind - you still feel the sweetness of the image and the fantasy.
Admit it, if it is the truth, Hashem's chosam is Emess. But the emess is that even though we may feel a pleasure from it - it is destructive to you and me. So we surrender it up like a korban.
I said the parsha of the korban tomid or the korbal olah many times early on when a lust memory came to my mind. I was not fighting it - I was sacrificing it up to Hashem as a rei'ach nichoa'ch. It is the inner meaning of the familiar segulah of saying "eish tomid tukad..." Pornography from the mind of a recovering sex maniac like me - is surely a very sweet rei'ach for my Tatty in Shomayim.
"ki ani l'tzela nachon - for I am mesugal to slip - umach'ovi negdi tomid" (tehillim 38:18) (Dovid haMelech meant something else of course. But for me, admitting that to Hashem - I am mesugal to fall, Tatty. That's why I need You so badly!" That's what He wants, of course. And it works. I know it works and so does every alcoholic and sexaholic in recovery anywhere in the world.
Give it up, you really don't need the sweet schmutz. Why fight with it? Wrestling with it 'to the death' is just a trick to hold onto it as long as you possibly can until you are done enjoying it. Let it go and let G-d solve the pain for you. It will hurt. But that's OK. You are not alone.
Hatzlocha!