Although it may seem a bit strange, adding (tongue) to the negative prompt is useful.

Specially trained for furry and dragon. The training picture is from e621.

extremefrenchkiss, french kissing, tongue out, long tongue, 2boys

(size difference), (open mouth), (interspecies) for human or (furry with furry) for furry is useful.

(anal, ananl sex, size difference) is distinctive.

I really want to do this in my dream.