No.
You can, however, use WiiXplorer to move files from a USB to an SD card, but that's about it.
Where in the heck did you hear you couldn't use a USB?? o.O
You can only use a USB device for Riivolution, but I warn you, USB loading on Riivolution is like a snail trying to do 200 laps on a racing track.
But for an accurate time, I would put it as 2-3x the regular loading speed. It's that bad.