Before you could by making doc happy with ammo/armor/guns to get 900 rep and then joining and leaving BoS infinite number of times to accumulate 4875435643 NCR rep.
Now it shouldn't be possible at all, killing raiders will bring rep only to -200 or to 0, not more.
Trading rep cap is 900.
You can FA guards/NPCs and never log out, because when you're logged in your rep won't degenerate, but it'll take some real life years to get a lot rep by FAing guards even if you have high FA skill with small CD and your friends will burst those guards 24/7.
Try to join different factions to see what reputation changes, may be there's some another exploit which isn't fixed yet. But I don't think there's, as most factions will only decrease NCR reputation.
There's also some way how to get over 900 rep, join some faction which lowers NCR rep, then get NCR rep to 900 by trading and then leave that faction so NCR will like you again and give you some boost, but leaving boost is always less than joining, so it means it's only 1-time boost and you couldn't accumulate your reputation.
So the only way is: FA guards non-stop, get something like 1 rep per FA. If you have 900 rep from trading, you'll need to FA only 601 guards! Start today, may be you'll do it before wipe.
Oh, also there were some changes in reputation, but I haven't noticed it yet, you still can shoot negative rep players, if you have >1000 rep gap between you and them, but I don't know what will happen if player have >=0 rep, probably you won't be able to attack them anymore.
Still I think you can shoot < -101 rep players if you have 900 rep, or may be < -301, as after -301 reputation says "Antipathy". The fact that you can shoot < -1000 rep players if you have positive rep is 100%, as I was trolling with my friend by this way long time after last update, a lot poor innocents died by guards when they attacked me too after my high rep friend shoot me and said that I'm failed thief. Even GM abused his powers and sent me to jail+glow after that even when it wasn't breaking of rules!
