You can use USB Loader GX. I use it on my softmodded 4.0u and it works great. Allows you to play games right off the USB drive and you can rip games to the USB also(takes maybe 15 minutes or less). Get it here and install to your wad file on your SD card. You might also want to download WBFS Manager 3.0 to extract the .iso to your computer. Get it here.
Do you have the homebrew channel installed? If so just place the usb loader gx .wad into your wad folder on your sd and install with wad installer. Should come up as a channel. If not go here