I trained this specifically on some of the wildest and most detailed hyperdick futa content I could find and the results haven't disappointed me.
Here's some tags I found useful in my prompts::
"futa only, huge cock, hyper penis, huge penis, veiny penis, long penis, very long penis, thick penis, veiny, pulsating, throbbing, veiny balls, urethral bulge, ejaculation bulge, testicle clench, precum, dripping, uncensored, full body, erection, unusual penis, ahegao"
(I should mention that the tag "futanari" has ended up a bit overtrained on the regularization class- it shouldn't ruin the result, but it might dramatically change the art style in an unexpected way.)
Unfortunately a lot of the training data had some minor censorship in it. If you keep getting some black lines around the tip, throwing terms like "censored, censor bars, black bars, black bar censors, blackbar censorship" should reduce the likelihood of getting them.