Check out Liberty University if you're trying to get just your flight ratings with your GI Bill, but no matter what you do, if you are trying to work part time and fly part time, your GI bill won't get you very far. You'll want to be flying full-time.
The GI Bill fiscal year resets every August, so if you sign up in the Spring and take accelerated courses (First half of Spring = 1st flight course, Second half = 2nd flight course), you can essentially use up your fiscal year budget of roughly $37k per year in one semester. They are way over priced when you look at pricing for all the ratings combined, but that's for a different discussion. Some of the flight schools where you can use the funds also jack up their prices... maybe because you're so limited with the GI bill. So those funds won't get you as many flight hours as if you had cash and shopped for a different Part 61 school down the street. Do your research before you commit to any particular flight school under this program (they partner with multiple schools in multiple states).
Example route you can take:
Spring 2019
First 8 weeks - Private Pilot I - $9000
Second 8 weeks - Private Pilot II - $5000
(You may need to take ground courses in conjunction, plus another course or two to collect BAH, raising your semester bill toward using 80-90% of your fiscal year private school budget).
Summer 2019
Maybe take Instrument Flight ($12000 at Liberty) if your GI months and money remaining allows, otherwise pay for this out of pocket
Fall 2019
First 8 weeks - Commercial I - $9000
Second 8 weeks - Commercial II - $9000
Out of pocket
Commercial III - $9000 (or do this Part 61 if it's cheaper to finish)
Finish all the rest of your ratings out of pocket
Those prices I listed are their advertised lab fees, not including other miscellaneous stuff you'd have to pay for out of pocket. All in all, you could get a large chunk of training accomplished if you're smart about it. If you wait until Fall 2019 to start, you'll probably not have access to GI bill funds from Jan-Aug 2020 while you wait on your fiscal budget to reset (even if you have "months" of benefits remaining).
If you already have your Private, then obviously shift the courses you sign up for. Here's their other advertised lab fees below ($90,500 total in fees just for the flight portion, not including ground school, books, checkrides, etc)... so not the cheapest option for folks without the GI bill.
Flight Instructor - $12,000
Flight Instructor Instrument - $7,000
Multi-Engine Flight - $8,500
Multi-Engine Instructor - $10,000