Find out whether your console is fat (in which case also find out whether it's NAND or NOR, you can do that via the model number) or slim (in which case ensure it's flashable, all 20xx and 21xx are, for 25xx perform a minverchk)
Go to the flash writer's webpage (NAND or NOR as appropriate - all slims are NOR; USB or HDD at your choice) and follow the instructions, for the USB variant you must put a file on a flash drive (that must be usable on the XMB) inserted into the port you select, for the HDD variant you must download a "picture" first from the exploit webpage
Then set the exploit webpage as the browser's home, reboot the console, and try performing the exploit (which isn't guaranteed to work reliably, it's a hack after all)
Once you successfully perform the flash writer, just update to a 4.84 CFW of your choice via USB (just like you did to install the hybrid 4.84/82)
From there you can install and run homebrew, including the kind that enables the QA flag and makes your console downgradable even on OFW (of course, once you have 4.84 CFW, there isn't much practical reason to downgrade in the first place!)