Hi everyone

I apologize if this topic has already been posted elsewhere on the site, I wasn't able to find it anywhere.
I have been looking on the internet and I can't really find exactly the answer I am looking for. I was wondering how new pilots right out of flying school build up their multi engine time to the amount requested by the regional airlines. Do most pilots rent the plane in their spare time, do they instruct on multi engine planes, are there entry level non regional flying jobs available?
Thanks in advance for any information you may have.