Hi Justin,
Two months is pretty quick to go from zero to proficient in the Quant but if you can really dedicate yourself it is certainly possible. If you're not going to take a class or hire a tutor then then the
Manhattan books are a pretty good option. On the positive side the
MGMAT books are pretty exhaustive and if you study the entire set you probably won't be missing any fundamentals but that said they are also long winded so there's probably a bunch of stuff in their that's not so important for you. But hey, nothing is perfect. With the books you also get access to the
MGMAT practice tests and at least for Quant they are very helpful.
In addition there is a lot of good stuff on the forums. Generally you can Google the first bunch of words from any official GMAT question and find a pretty good explanation.
I'm releasing an 11 week GMAT schedule. It assumes some basic math proficiency from the start but maybe the structure and the organizational ideas will be helpful to you:
https://atlanticgmat.com/gmat-schedule-intro/Getting your Quant up and running is going to a challenge and it may take a second for things to click. That's normal for people who haven't done math in a while. Just stay organized and stick with it.
Let me know if you have any questions!
Happy Studies,
A.