Use flash slave (called SU4). This flash slave is put on flash hotshoe to trigger the flash by camera's flash output. Some flash like Nikon SB-800 does have internal SU4 function, which can be triggered by compact flash camera without need flash slave.
Yes, use a slave adapter, and have the flash on the PnS covered with an IR (Infrared) filter. The CCD would be less sensitive to IR ray, but the slave adapter would be 100% sensitive. Make sure the F stop and ISO setting on both the camera and flash unit tele. you now bounce to ceiling, side way, or even rear corner for group shot, if yours' external flash is powerful enough !;p in "A" mode
The Infrared filter for the flash can be easily made, by processing a roll of unexposed slide film. I've alot of left over, to share with you free, those whom has interest to try. Please PM me
I've a Fuji F30, which can operate nicely on ASA800, with the aid of a very old Metz 40MZ2, I can easily shoot under F5.6, even F8 (ASA800 !). This is impossible in the good old days, whilst the usable ASA restrict to 100 or 200 !