Hi all, I am still relatively new here but here are the things that seem to be working or have been helpful.
Very early, when I first found out about OG/W just after BD, I said "she must be something really special" H has said multiple times that that really cut deep because I would "win" on just about every point. It was helpful for me to assess where H was at, in that he doesn't seem to feel like he deserves me and has affaired down as a way of seeking equity in his personal relationship. Of course, we all know that this is kooky logic and only brings him further into the abyss.
Another thing that seemed to shift his negative actions was to use something from our past, during the days of courting, we used to write each other lovely packaged cryptic letters. I chose to write one to him, it was very positive and focused on his quality attributes as well as a few impressionable moments from our relationship. This was definitely a dodgy move. My H is very broken and his self esteem is totally down the toilette. In other cases I don't think this would be helpful, but for us it helped to pull him out of a blaming mindset and started to remind him that I am not the enemy and that we did share a beautiful past. I slipped it into a book of his and he got to read it on the metro while traveling to work (where he would likely see the OG/W which was intentional). He said later that it really hit a nerve.
Generally, it seems to help my H to not put any pressure on him. The more I act in opposition to what he expects or thinks he deserves the closer he steps towards reconciliation. Again, I am still very early in this so I am likely up for some much rougher water. Time will tell.