[Saphire]

Lello, if you need the pre-flash to set off your other slave flashes I may be able to help. I used the top of a canister in white the same density as a diffuser, on one side I used black duck tape to mask it out totally. I pop it over the on camera flash with the black side facing forward this throws the light backward which doesn't effect the exposer but still triggers the slaves. You can also use it turned round white forward to act a diffused light.