it really depends on how screwed up the wii is. if it is a brick caused by a update from a wrong region, just autoboot a game with a newer update for the right region.
if you screwed it up by other means, you can try to take any game ISO, swap the main dol in the game with a wadmanager dol (renamed to main.dol), patch the ISO to use 249 (assuming that the wii has 249 installed), set the modchip to autoboot, and cross your fingers. if the wii isnt too screwed up, it should boot into wadmanager and you can install wads to undo what you did.
you can also use this way but put other dols in the ISO depending on what you want to do. there is not a magic "fix the wii" ISO.
also, LMFAO at another "my friend" bricked his wii. nobody ever bricks their own wii. its always a friend or a uncle.