I don't have an additional flash so I can't answer your question on how to set your flash, although some of what I've read has suggested bouncing the flash off the ceiling. But... have you tried increasing the ISO and using a large aperture? I'm not sure that your current lenses will open up quite wide enough, but if you were really interested in doing this sort of photography often, you may consider picking up a lens with a maximum aperture of f/1.4 or f/1.8 depending on your budget. Hopefully you get someone who can answer your flash questions though
