I have one of those bounce cards for my 60CT-2. As Bob Salomon says in the LF thread, those cards need a bit of gaffer tape to hold them in place securely. They do work well, though they are limited by their size. If there is no ceiling or wall or other thing to bounce off then they are handy. You can get bigger rigs that mount on the camera - it all depends on what you are happy with. You can be quite creative once you have the card holder by making different cards and reflector/diffusers.
The problem I find with the small direct secondary flash units is that they can overpower the bounced light, even when on the low power setting. I have an ND+CTO filter permanently taped over the ones on the flash guns I have that have them (contorted explanation). If you are using something like the bounce card, the source is close enough to the lens axis that the secondary flash isn't required, as far as I'm concerned.
If you are bouncing off the ceiling then I prefer a small card, or my fingers (an old trick), behind the main upwards-pointing head to bounce just a touch of light straight ahead. If you are bouncing off the wall behind you then you probably don't need the secondary flash either.
The softening effectiveness of any reflector or diffuser can be assessed by imagining or observing the apparent size of the light source from the subject's position. Dark Ray-Bans are useful.
Best,
Helen