Dirty flashing refers to the practice of flashing a custom ROM on top of an existing ROM already present on your phone.
You have two types of dirty flashing : The normal type one, where the dirty flashing is done during the upgrades (Example : from ArrowOS version yesterday to ArrowOS version today) and the second type is when you go nuts and just flash the ROM on top of a non compatible ROM (IE: Flashing ArrowOS over any other ROM you previously had).
Once again, dirty flashing is only recommended when your current ROM and the one you are flashing are compatible.
In our case that meas when you are upgrading to a newer version of ArrowOS.
How to do that:
Boot into your recovery Flash the OS update zip file Reboot!
Congrats, you’ve done the dirty 🙂