Hey Roger, great question!

Set the Direct Mix to 100%, then use the Effect Level to bring up the level of the reverb. In effect, the Effect Level becomes the Wet/Dry mix control.

Of course, they give you those extra parameters so you can experiment and come up with different sounds, so set the Effect Level to around 35%, then check how everything sounds with a bunch of different settings for the Direct Mix control.

Hope this helps!
Thx,
Mike