How do you get infinitd bullet and other items by witch buttons to push for Mario kart wii and ds?

Well, actually, you can't. Bullet Bill is only obtainable when you are in 12th, 11th, 10th, 9th or 8th. The only alternative to bypass this is to hack using the Homebrew Channel application Ocarina, which I don't recommend you to do, since the majority of the online Mario Kart Wii community is against hackers that hack to win.