How to Soft Mod A Fat PS2 W/O Action Replay

Okay so i have a fat ps2 with an ide hdd and the network adapter. I want to soft mod it to play burned games/emulators, etc. I dont wanna go out and spend money on action replay/gameshark/or codebreaker. Cuz its too damn expensive now a days… so if anyone can help me it would be highly appreciated. and remember it is a fat ps2 with a harddrive in it not a slim…i heard its easier to do on the fat.