I find Bronx to be pretty quick to get to it if the females are willing...I'll stick a girl in with him for a few until I see him try...if she won't let him I take her back out and try again in a day or two...I have trouble seeing ovulation...so I just try every couple of days until he gets her
I've got one female gravid this way (one hasn't let him breed yet after 5 or 6 tries, and the other females he's gotten gravid were made gravid while he was actually being housed with them). I figure its really the safest way, because if they get into a big fight I can cut in and separate them (hopefully without any injury to myself...lol).