If Griot`s Rubber Prep doesn`t do it, I use a rubber-friendly compound to "get down to good rubber" and then do the Rubber Prep. That`s worked fine on trim that appeared *far* beyond salvageable (and it looks like yours isn`t *nearly* as bad as what I`ve fixed), though it can take a while (not just an hour, plan to be at it for a while).
Some people like IPA, but it`s seldom potent enough for me (if things are that OK the Rubber Prep alone is fine).
Then I seal with Ultima Tire&Trim Guard Plus.
Like WingCommander, I like to use demoted MFs, but for the aggressive work you might experiment (carefully!) with cotton as it`s more aggressive. Just watch that it`s not *too* aggressive as you don`t want to mess up the texture too severely.