I had another idea while working on the barbed penis Lora. I got pretty good results around 0.5 so you can run this weaker as needed. Adding testicles to the prompt helps a lot in some situations so try that if you have issues.

Example Prompt:

(dark_skin:1.2), horse_girl, fully_sheathed, <lora:FullySheathedV1:0.5> testicles, looking_at_viewer, small_breasts, nipples, blush

FYI as per usual this dataset contains zero men so if it works for men, great but I'm not testing for it.