My wife has had one bull who was comfortable enough with me to tell me directly what to do. Only once did my wife tell me (at his command), "you better obey my bull," and he took it from there. He told me how to dress her (and when to undress her) for him, had me suck him and get him hard for her, told me to lick her pussy to get her wet and ready for him, to guide his cock into her pussy, to hold her ankles apart for him, to go sit where he wanted me so I'd be out of the way while he drilled her, or so I'd have a clear view of him splitting her open, to lay under her and lick her clit while he fucked her, to open my mouth so he could cum in it, and then to snowball with her, etc., etc., etc. Tenderly French kissing my freshly fucked wife with a big mouthful of her bull's hot cum, while he told me things like, "she finally got a cock that satisfies her," or being told I was to stay locked and go down on her every night until their next meeting, but that I had to stop right before she came, because my wife's pussy "belong[ed] to him now," was indeed an extremely submissive period for me.
Another guy we met on a trip we took together had me do some of the same stuff, but he told her what he wanted her to make me do. This was a one-off so it didn't have quite the intensity as her first regular bull's gradually increasing (and eventual total) domination of both of us, but it was surprisingly potent in his own way. She was fully submitting to him in relaying his commands to me, and I felt very dominated. I think it was partly because I was obeying both of them at once rather than one at a time, and partly because he didn't talk to me, even though I was right there beside them and could obviously hear all the things he was instructing her to have me do. I'd hear his deep voice describe what I was about to be told to do, creating extremely self-conscious anticipation, and then my wife's firm voice, with all the devastating authority she always has over me, despite the added element of eager compliance she slathered on to please the man she'd found to fuck her that night.
I'm not sure I have a preference between taking orders directly from a man who fucks my wife, or indirectly, via my wife's lips. In the first case, it was a gradually deepening exploration of the cuckold rabbit hole her bull was leading us down. In the second, a very clear hierarchy was established nearly instantaneously. It left no room for doubt that this man was taking full control, and she was going to make sure he had his way with both of us.
Her current regular bull has no desire to play with me, but he gets a thrill out of getting her extremely worked up and horny, and making her do or say slutty things that aren't part of her typical behavior. I honestly think he gets a kick out of knowing he's done things with her she has never done with me, and enjoys sending me evidence to drive me crazy. I don't have very direct role with him, but the sex they have is unbelievably hot and carnal, the content I receive is jaw-dropping, and my interactions with him are enjoyable. Once he told her I'd been a good cuck and that she was to reward me with a blowjob when she got home. That obviously didn't fit our normal submissive husband model, but I did think it was very thoughtful of him, and she was sure to be very vocal about the differences between my cock and his. She reminded me several times that, it wouldn't be the hungry kind of cock worship he gets, and that she was only doing it to show him she was an obedient slut for him. So it wasn't a complete reversal of our usual roles, and I certainly wouldn't complain if it happened again.
We don't have too many hard expectations for how her bulls should interact with me, as long as there's room for her to include me in her adventures, and for my naturally submissive tendencies to be explored in some capacity. She's had a couple of basic fuck buddies here and there, but we both definitely prefer it when a guy she's seeing actually enjoys having me involved. It absolutely doesn't have to include bi play of any kind, but it's nice when a man at least gets a clear thrill out of fucking a married woman, while her husband facilitates the rendezvous or simply has to take it all in. Guys that just want to fuck her, and would be equally happy if she were single, tend to bore her pretty quickly and don't seem to last very long.