(PS2 version)
Through game farming - Go to the Royal Hunting Ground at night. The trick is to fight when you encounter three or more Metal Slimes. When you encounter fewer or none, choose the flee option.
Use Metal Slash with Hero and Angelo, and equip them with Liquid Metal Swords if possible. If not, use your strongest weapons.
For Yangus, use only Executioner and equip him with the Conqueror's Axe if possible. If not, use your strongest axe.
The best way to use Jessica is to utilize Timbrel of Tension if you have it. If not, use Accelerate.
It becomes easier when you gain levels.
Post-game farming - Same as the above text, but go to Slime Island at night instead.
Now, for the actual farming part, you need to engage in battle only when you encounter 3 or more Liquid Metal Slimes, King Metal Slime, and Liquid Metal Slimes, which, for me, are by far the best possible enemies for grinding in the whole game. Or, of course, two King Metal Slimes. They are very tricky to beat. In all my gaming in this game, I've managed to beat them both only once.
Don't forget to choose the FLEE option if you encounter fewer or different enemies. This is the most important rule to farm quickly.
I will not bother you to show you or guide you to the specific locations, making the described weapons and all other specifics, which are not described here. There are a lot of guides out there, so I'll give you the basics.
That's it. You are welcome.
