I've been doing it like this on my internal drive:
Name your GameShark ISO similar to the following: dev_hdd000/PSXISO/XXXISONAME1.ISO <---this is your GameShark ISO
Name your game ISO similar to this: dev_hdd000/PSXISO/XXXISONAME2.ISO <---this is your game ISO
Place them into the same game folder.
Example:
Game
Resident Evil: Directors Cut.
Naming structure
GameShark ISO: /dev_hdd000/PSXISO/Resident Evil Directors Cut/REDC1.ISO
Game ISO: /dev_hdd000/PSXISO/Resident Evil Directors Cut/REDC2.ISO
(Yes, this means you will need a copy of your GameShark ISO in every game folder. This means you will need multiple copies of the same ISO on your drive.)
You'll need webman, not multiman. (I hear multiman also allows you to open a web browser and point it to your PS3 to disc swap, but I haven't tried.)
- Mount GameShark with webman and run it from the disc icon in XMB.
- Browse the game list until you find your game and select your cheats, then select Start Game.
- Using any device with a web browser (tablet, smartphone, pc) enter your PS3 IP address as a web address. You'll be greeted by the webman web interface, assuming you have the web server active in the settings. Note: both the PS3 and the device you are using to access the web server MUST BE on the same network or it won't work.
- Click on games then click the UNMOUNT button.
- Click on games again, then PSXISO. Browse for the game you want to cheat on and click the game. On the PS3, there should be a webman notification indicating the new game has been mounted. In case it doesn't and it shows an error on the webman web interface, there will be a clickable URL next to "Error!", click that and the game should mount.
- Press O on the PS3 controller to boot the game with the selected codes. If you get a black screen, one or several of the codes are causing the game to crash. Try disabling some of them until it boots correctly.
Some notes:
The only version of GameShark I've been able to get running properly was Version 5. All others caused a black screen with music still playing or crashed back to XMB. Not all games are compatible. Some just don't work at all. It will black screen all the time.