While the undubbing projects exist for both systems, I never found a tutorial online that explains how the process goes. So, does anyone have some good advice?
I know about PSP. It depends on the game... There are tutorials of specific games which are more difficult (like Final Fantasy Dissidia or Kingdom Hearts: Birth By Sleep), but you can do it in general. You just need to use UMDGen (v4.00) and both JAP and USA/EUR versions. There are some tutorials on YouTube.