When I first started with detachment and boundaries, it helped for me to see detachment as removing my emotions from the things he did and by boundaries as protective actions for me to limit the kind of interaction I had with him.
I wasn't in a bubble denying the behavior around me, but I did keep those emotional buttons he liked to push out of reach from him and I did detour the conversation, and even left the conversation entirely when he was making grabs at them.
For example, detachment meant that when he came hom in time to eat a meal with me instead of staying out to the wee hours after work drinking, I did not stew in anger over all the other meals he missed, but rather stayed in the moment and sat down to eat with him as any other couple would. Asked about his day. Told him any interesting news of mine. When he had the shakes from not drinking that night and would spill his food, I didn't react safe to say, you okay?, you want my napkin? When he rolled his eyes while I was talking or made angry remarks that signaled his mood was turning dark, I said nothing, no sigh, no snapping, no rancor. I got up with my plate and left the room. For all he knew I was getting another napkin from the kitchen. I just never returned. My boundary was crossed and I acted on it accordingly. In the end the meal, for what we had of it together, was pleasant. What time we spent together was nice and I left it at that no holding a grudge because it wasn't more.
I equate it to watching a scary movie and covering your eyes for all the gory parts and then refusing to imagine what's happening on the screen either. That way you can enjoy the film without having nightmares later. And if all else fails, get up, take your popcorn, and go down the hall to that G-rate film for a while. Let the horror movie go on without you.
I didn't ignore him because that takes effort. Instead, I lived with him the way I chose to. Pleasantly, civilly, with respect, and caring. When he did the same, I stayed in the moment and things felt peaceful, normal. When he chose to act any other way, I got out of the way. As I got more skilled in recovery, he learned it was fruitless to keep trying to cross those boundaries or access those emotional buttons again. He tried many tactics and some things caught me off guard, but I was able to recovery quickly and keep at it.
Hope this helps.
Alice