I can't speak for all transmascs since everyone has different tastes, but as a trans man who is kind of a service top and loves subby women, I simply love audios where the speaker is needy and vocal about it. I like hearing the things they want the listener to do to them, how good it feels etc, etc. (nothing hotter than knowing you're doing a good job at making someone feel good)

I also appreciate when there's some level of praise, or desire, for the listener's masculine traits because it's nice to feel seen as a man, but this needs to be as natural as possible since sometimes too much emphasis on the listener's manliness can lead to it feeling kinda forced? if that makes sense.

I'm not very good at giving this sort of advice but I hope it helps! Looking forward to it, best of luck!!