If you can get hard and stay hard in a chick's hole while several other guys are lustfully rubbing against you, if you can cum on demand and not early, if you aren't particularly picky about what you stick you cock into, then there's probably someone who will hire you, after you break in.

The breaking in is the harder part. A lot of guys claim they can do it and then fail to perform when the camera and payroll is rolling so there's a reluctance to try any new guy. Remember that the rest of the cast & crew are being paid while a guy struggles - that's expensive, especially if he can't finish the scene as desired. A girl only needs to provide holes for a shoot but a guy needs to perform.

As was said it's about the girls. As long as it's not too distracting from the girls the problem of getting in is going to be the usual one of finding someone willing to try a new guy.

(a lot of guys get in by getting a cute girlfriend with several accommodating holes and tricking her into doing porn, only with them. Sometimes it works if the girl is hot or into anal gangbangs or other circus acts)