I barely even used Twitter at the time, but I sent my portfolio (along with about 100 others--I later found out). Shortly after that, I was selected to work on this pitch! I was actually his second pick, but the first pick's schedule didn't work out. That was my introduction to Jim Zub.
The pitch wasn't picked up unfortunately, but I stayed in touch--checking in every few months. Jim's long-time letterer Marshall Dillon forwarded my name to Jim again in September 2015 to work on the GLITTERBOMB pitch.
Every series I've ever worked on started the same way.
I colored a four page short for Tim Seeley for Black Mask Studios in late 2013 on the recommendation of a penciller I'd worked with previously on... yep, another short. I colored yet another short written by Tim for IN THE DARK after trying out for Rachel Deering. I wouldn't have known about that project if it weren't posted on Facebook by one of the first writers I ever collaborated with -- Magnus Aspli. I started coloring Tim's HACK/SLASH a few weeks after all that.
Another four-page short I colored led into a on-going monthly series. This hasn't been announced yet. More on this soon.
So it's a small industry. Everybody seems to know everybody else. I guess the moral of the story is that no job should be too small. You never know where it might lead. Befriend other creators. Hit your deadlines. Be nice. Be patient.
If it takes you five years to work for a major publisher, are you still interested? That will separate most beginners that "make it" from the one's that don't.
I hope this helps someone! Best of luck. :)